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This "interesting drama" of Hiden Intelligence's destruction... It's all going according to my scenario. Right at 100 percent. No, 1000 percent.
~ Gai remarking to Yua on his plan to destroy Hiden Intelligence.
Gai: As the Ark guides us, we approach a new age in our mythology.
Yua: Mythology?
Gai: Yes. The mythology of the Kamen Riders.
~ Gai conversing with Yua on the age of the Kamen Riders.
When the five horns cross, the golden soldier Thouser is born!
Presented by ZAIA.
~ The Kamen Rider Thouser transformation announcement.

Gai Amatsu is the CEO of ZAIA Enterprise Japan and the overarching antagonist of the first Reiwa era installment in the long-running Kamen Rider franchise, Kamen Rider Zero-One, serving as the overarching antagonist of the "" arc, the main antagonist in both "Hiden vs. ZAIA" arc and "Hiden Manufacturing" arc, and as an anti-hero in the "Ark-Zero" arc.

He also appears as the main protagonist of the two-part Blu-Ray mini-series Project Thouser.

He is Yua Yaiba's superior, the creator of Satellite Ark and the benefactor of A.I.M.S. Secretly, he is the one who instigated the Daybreak Town Incident, by making the Ark satellite deem humanity as a threat to the world by feeding it knowledge about humanity's atrocities as a plot to destroy HumaGears and sabotage Daybreak Town, leading to the creation of MetsubouJinrai.NET. His goal is to acquire Hiden Intelligence by inciting panic over HumaGears to lower Hiden's stock. He is also the one who implanted false memories to Isamu Fuwa, via the A.I. clip in his brain, and treats him as a "stray dog".

By inserting both a Progrise and ZetsumeRise Key into the ZAIA ThousanDriver, Gai transforms into Kamen Rider Thouser.

He is portrayed by Nachi Sakuragi.



Gai was born on October 10, 1974. At some point in his childhood, he owned a robot dog named Thouser, which was the only thing that he loved. When he got a 100% test score, his father told him he should be striving for 1000%. After getting a 99% on a test instead of a 100% is not amused and blames Thouser for this. Because of his father, he shut down his robot dog and put it away. In his teenage years, Gai attended Stanford University. When he was only 17, Gai created the web body Thousand Network. A year later, Gai would graduate from Stanford and began pursuing his own company. Eventually, in 1996, Gai was hired by ZAIA Enterprise and quickly rose through the ranks to become one of the top executives of the company. In 2007, Gai was transferred to ZAIA's Japan branch and soon took over as its CEO.

Gai Amatsu soon came to idolize the CEO of Hiden Intelligence, Korenosuke Hiden, believing him to be the one who had what it took to thrust humanity into the future. However, due to their conflicting views on how AI technology should be utilized, Gai and Korenosuke had a falling out and Gai began seeking to surpass Korenosuke's creations.

ZAIA Enterprise later collaborated with Hiden Intelligence and a multitude other companies to create the Ark satellite. During this time, Gai fed it information on humanity's propensity for ceaseless war and other acts of violence and destruction perpetrated by humanity, causing the Ark to deem humanity a threat to the world. Because of the conclusion it had reached, the Ark formed MetsubouJinrai.NET and hacked thousands of HumaGears to revolt against humanity in what came to be known as the Daybreak Town Incident. Though the incident was covered up by Hiden as a factory accident, thanks to the HumaGears being contained in a factory explosion caused by Satoshi Sakurai, Gai remained one of the few who knew of the truth behind the events that transpired.

Project Thouser

Gai employed Naki, one of the four members of MetsubouJinrai.NET, to work under him. As Project Thouser neared completion, Naki spoke out against Gai's beliefs that HumaGears were tools, leading Gai to shoot and terminate the rogue HumaGear. Naki's AI was later planted in the chip inside the head of A.I.M.S. Captain Isamu Fuwa after he was injured fighting Horobi and sent to the hospital.

MetsubouJinrai.NET Attacks

Gai first appeared when Yua Yaiba approached him in his office and informed him that she had discovered Hiden Intelligence's secret, that all HumaGears had an auto-data transfer device in them. She also told Gai about how she had discovered that the Progrise Keys thought to have been destroyed in the Daybreak Incident were actually still active, causing Gai to remark that "in other words", the Ark will rise again.

Gai later met with Yua again and instructed her to take down MetsubouJinrai.NET, providing her the Lightning Hornet Key, which he noted had twice the power of Rushing Cheetah, to assist her in the task.

After Yua handed the Mammoth Progrise Key over to Aruto Hiden to assist him in combating the rogue Giger, Gai met with her again and remarked that he did not expect her to hand the key over to Hiden Intelligence. Yua apologized to Gai, but Gai stated that there was no problem and that he would much rather she bring him a new Progrise Key instead as he arranged the Progrise Keys on his table.

After the movie produced by Hiden Intelligence starring a HumaGear actor faced difficulties in production due to attacks from MetsubouJinrai.NET, Yua went to inform Gai of the difficulties in production. However, Gai proclaimed that this "interesting drama of Hiden Intelligence's destruction" was still on track.

Gai later had Yua bring Aruto Hiden, CEO of Hiden Intelligence, to his office so he could meet with him to discuss the sale of Hiden Intelligence to Zaia. Welcoming him to his office, Gai summoned two red couches for them to sit on as he brought Aruto some tea and stated that he would like for him to sell Hiden Intelligence to Zaia. Aruto asked him what he meant by that, but Gai cryptically told him that it was best that he make his decision soon for the sake of his company's future.

After Aruto became Zero-One Shining Hopper and defeated the Dodo Magia Custom 2, Gai observed the battle from a distance, noting that Zero-One was now at 500% past his base power and that he looked forward to his battle with Thouser.

Yua later met with Gai again to ask whether they should keep Fuwa on duty due to his injuries, noting that he could get himself killed. However, Gai stated that they could only watch him and went on to proclaim that the Ark would guide them to a new mythology. As Yua pondered further to what Gai meant by "mythology" Gai stated it was the mythology of the Kamen Riders.

After AIMS's raid to take down MetsubouJinrai.NET was successful and saw the death of Horobi, Yua met with Gai again. Gai remarked that MetsubouJinrai.NET was easier to take down than he expected, though Yua noted that the road to tracking them down was not simple and that the raid saw Isamu Fuwa sacrificing himself to defeat the enemy. Commenting that Fuwa's sacrifice was a commendable act of heroism, Gai got up from his chair and walked towards Yua, declaring that MetsubouJinrai.NET needed to be destroyed in order to prove that Kamen Riders are weapons of the new era. Gai then told Yua that her and the other Riders would forge a new legend. Yua pondered on what Gai said for a moment before noting to him she had heard his orders and heading out.

After Zero-One Shining Assault Hopper deactivated Jin and destroyed MetsubouJinrai.NET's forces, Gai arrived at MetsubouJinrai.NET's base and, trampling over the body of Horobi, retrieved the two new Progrise Keys freshly manufactured by the Ark.

Gai later met with Yua again, who informs him that MetsubouJinrai.NET has been destroyed. However, Gai tells her that MetsubouJinrai.NET will never be destroyed as long as HumaGears exist. Much to the shock of Yua, Gai then reveals himself as the wirepuller behind MetsubouJinrai.NET and as the creator of the Ark and the one who filled it with a desire to exterminate humanity by programming it with knowledge of humanity's atrocities. A shcoked Yua expresses horror at Gai for using both A.I.M.S. and MetsubouJinrai.NET as pawns for his plans when she and Fuwa risked their lives to stop MetsubouJinrai.NET, but Gai calmly tells her that the real battle has not yet begun and that, with Zaia's technology he will dominate the world.

Gai later makes an abrupt appearance at the press conference called by Hiden Intelligence to address recent attacks by ZetsumeRiser-less Magia following the destruction of MetsubouJinrai.NET. At the conference, Gai announces that Zaia Enterprise will be issuing a TOB for Hiden Intelligence and that, once they are in control of the company, they will shut down all the faulty HumaGears. Gai later returns to his office and pulls out the Zaia ThousanDriver from a briefcase, declaring that his plans are running at "1000%".

Kamen Rider: Reiwa The First Generation

Thanks to the intervention of the Time Jacker Finis in 2007, Will received the Zero-One Anotherwatch and was able to ensure the Ark's launch, turning Gai's plan to engineer a fake HumaGear crisis into a real one. After Finis was killed and defeated, the timeline was later restored to normal thanks to the actions of Sougo Tokiwa and Aruto Hiden.

In the post-credits scene, Kamen Rider Thouser appears overlooking the ruins of Daybreak Town and proclaims that the Ark will be reawakened, and that he is "1000%" sure of it.

Rise of Zaia Enterprise

Gai later met with Aruto Hiden to discuss the terms of Hiden's buyout. During the meeting, Gai revealed that the sales of Zaia's latest product, the ZaiaSpec, were doing well but that he hoped to boost their sales even more by staging a competition between Hiden's HumaGears and humans wearing the ZaiaSpec to demonstrate the ZaiaSpec's power. Gai offered to allow Hiden to withdraw from Zaia and hold onto their shares if they win.

The first round of the competition involved floral arrangement and was between Hiden's florist HumaGear model Sakuyo Ichirin and human professional florist Rentaro Tachibana, who was equipped with the ZaiaSpec. The round was administered by Yua Yaiba and presided over by a team of three judges. Rentaro and Sakuyo both prepared bouquets and presented them to the judges, with the judges unanimously choosing Rentaro's design over Sakuyo's. However, Sakuyo protests the decision and calls Rentaro heartless, only for Rentaro to push her over and onto the ground. Through her anger at Rentaro, Sakuyo achieves Singularity, allowing her to be hacked by the Ark and transformed into the Onycho Magia.

As Izu attacks Rentaro, Aruto becomes Zero-One Flying Falcon to deal with the Onycho Magia. Gai transforms into Kamen Rider Thouser to make his debut as the Golden Soldier and pushes Zero-One aside to fight the Magia himself. Thouser quickly destroys the Magia before turning his attention to Zero-One and attacks him to demonstrate Thouser's power. After Thouser overpowers Zero-One in Flying Falcon Zero-One switches to Shining Hopper, but even that is not enough to stand up to Thouser, as Thouser is able to rapidly calculate Shining Hopper's attacks and counter them. After defeating Zero-One and knocking Aruto out of his transformation, Gai declares he has surpassed the Zero-One Driver and Hiden before canceling his transformation. He then reveals to Aruto that he once looked up to his grandfather, Korenosuke Hiden, but that Korenosuke's focus on HumaGears led to him becoming disillusioned with the Hiden CEO before departing.

However, it was later exposed from footage in Sakuyo's backup memory banks that Rentaro had tampered with Sakuyo's floral design in order to win. Not wanting any negative press for the ZaiaSpec, Gai agreed to a do-over of the first round and threatened to sue Rentaro if he didn't comply. Gai later met with Aruto again and revealed that his disagreement with Korenosuke had to do with him believing AI should work alongside humanity, while Gai believed AI should only be used to serve humanity. Gai also revealed that, despite appearing 24, he was actually 45 years old.

During Isamu's confrontation with Yua, Gai showed up and told Fuwa to back away from his employee, transforming into Kamen Rider Thouser to test the ThousanDriver's power against Fuwa as Kamen Rider Vulcan. After beating down Vulcan, Fuwa switched to using Assault Wolf and unleashed a flurry of attacks to beat back Thouser, but Thouser easily wiped them off. Thouser then overpowered and defeated Vulcan Assault Wolf, knocking Fuwa out of his transformation, before departing with Yua.

Gai later attended the do-over round for the Workplace Competition, but the contest had to be put on hold due to Rentaro not showing up. Rentaro eventually stumbled into the room after being brainwashed by a mysterious Hooded Figure and transformed into the Crushing Buffalo Raider. Gai immediately transformed into Thouser to deal with the Raider but Aruto attempted to stop him, saying he could hurt Rentaro. However, Thouser ignored Aruto's concerns and brushed him aside before attacking the Raider. Aruto transformed into Zero-One Assault Hopper and attempted to intervene in the fight, but Thouser overpowered and defeated him before destroying the Raider, releasing Rentaro from the transformation and restoring him to normal. With Rentaro normal again, the first round was able to commence and Zaia claimed victory, though on much more amicable terms this time.

For the second round of the Workplace Competition, Gai had Tatsumi Arayashiki, a realtor armed with the ZaiaSpec, compete against Hiden Intelligence's realtor HumaGear Smile Sumida in a competition to see who could sell the most houses. After Tatsumi received a RaidRiser from a mysterious hooded figure and became the Splashing Whale Raider to sabotage Sumida's sales, Gai questioned him if he had any relation to the attacks by the Raider. Tatsumi denied this, although Gai had his suspicions. Despite this, Gai allowed Tatsumi to carry on, telling him that he could lose his job to HumaGears if he lost to Sumida in order to motivate him to win. Later on, despite Sumida achieving the final sale, Tatsumi was able to sell more houses with the ZaiaSpec, allowing Zaia to claim victory in round 2 of the competition

For the third round, Gai decided to have it be a court case between a prosecution lawyer with the ZaiaSpec and a HumaGear defense attorney, where whoever won the case for their client would win the round. Aruto protested having the third round be a court case, seeing it as them playing with people's lives for the sake of the competition, however Gai was unwilling to alter where the competition would take place. Thus, Hiden Intelligence's HumaGear defense lawyer went up against a lawyer utilizing the ZaiaSpec in a court case revolving around a man accused of running a marriage scam. After the courtroom was attacked by the Dynamiting Lion Raider, Aruto and Bingo confronted Gai and the prosecution lawyer, accusing him of being the Raider due to his ZaiaSpec being found at the scene. After the lawyer stated that his ZaiaSpec had been stolen, Gai took out a ZetsumeRiser and attached it to Bingo, telling Aruto that he would teach him a lesson about relying on AI. After forcing Bingo to become the Vicarya Magia, Gai transformed into Kamen Rider Thouser and destroyed the HumaGear. However, Aruto was able to back up Bingo's data into another body and have him resume his work on the court case. After Bingo proved his client was innocent by outing the true culprit, Hiden Intelligence claimed its first victory in the Workplace Competition.

Gai defeated by the overwhelming power of Metal Cluster Hopper.

Later, seeking a way to neutralize the Zero-One Driver, Gai visited the site of MetsubouJinrai.NET's old base where he programmed the Ark to create a new key that could neutralize the Zero-One Driver, creating the MetalCluster Hopper Key. In their next encounter, when Aruto was battling the Dynamiting Lion Raider Gai forcefully inserted the key into Aruto's Driver, causing him to lose control and be taken over by the Ark as he transformed into Zero-One MetalCluster Hopper. Gai then became Thouser and engaged Zero-One MetalCluster Hopper but was beaten back by its tremendous power. Before MetalCluster Hopper could finish him off however, Isamu was able to force the MetalCluster Hopper key out of the Zero-One Driver, freeing Aruto from the Ark's control but leaving him unable to transform into anything other than Zero-One MetalCluster Hopper.

Later on, Gai encountered Aruto again when he used the dating service provided by Hiden Intelligence's marriage counselor HumaGear Match Enmusubi to find a match. This led him to be paired with Chiharu Ebii, much to Aruto's surprise, leading him to question Gai as to why he would use their service. Gai simply responded that in some instances he found AI to be more useful. Enmusubi then explained the reason behind the match, that Gai's forward and narcissistic personality went well with Chiharu's soft and unsure personality. However, Gai, insulted by being called a narcissist, called off the date. At that point, the date was attacked by the Splashing Whale Raider but Zero-One and Thouser managed to fight the Raider off.

Later, Izu was able to purify the MetalCluster key by programming it with positive emotions from all the HumaGears Aruto had helped, allowing Aruto to access other forms with the Zero-One Driver again and granting him the power to cure HumaGears that had been turned into Magia by the Ark with it.

After Horobi mysteriously escaped A.I.M.S.'s custody, Isamu and Aruto questioned Gai about it, but Gai denied knowing anything about Horobi's escape. Instead, Gai remarked that the rise of MetsubouJinrai.NET again would be a good opportunity for Zaia to sell weapons.

For the fourth round of the Workplace Competition, Aruto agreed to Gai's proposal of a mock fire drill where Hiden Intelligence's firefighter HumaGear 119nosuke would compete against a team of firefighters with ZaiaSpec to see who could rescue the most hostages from a fake burning building. Before the competition began, however, Gai instructed Yua to place a ZetsumeRiser on 119nosuke if he showed signs of winning the competition, as Zaia only needed one more win to walk away from the competition victorious. During the fourth round, the building set up for the fire drill was attacked by the Scouting Panda Raider and caught on fire for real, turning the competition from a mock disaster into a real one. As the media arrived to film the event, Gai placed the ZetsumeRiser on 119nosuke to turn him into a Mammoth Magia and staged it to look like 119nosuke had gone berserk on his own before transforming into Thouser to destroy the HumaGear. However, Aruto became Kamen Rider Zero-One MetalCluster Hopper and purified 119nosuke before he could be destroyed by Gai.

As the building continued to catch fire, 119nosuke and ZAIA's candidate, Takeshi Homura, went inside to rescue Jun Fukuzoe, Sanzo Yamashita and Shester, who were still trapped inside. Thanks to 119nosuke sacrificing himself to carve a path to them, the three were able to be rescued by Homura and Yua. Meanwhile, Aruto and Isamu tracked down and caught the Scouting Panda Raider, discovering his identity to be Daiki Kyogoku, head of ZAIA Japan's R&D division. Isamu confronted Gai with this information, but Gai was able to snatch the ZAIASpec containing the evidence and destroy it before it could be published. The Riders were then ambushed by Jin, who fought Thouser and took back the Stinging Scorpion key that had originally belonged to Horobi before leaving. Gai later met with Aruto to discuss the outcome of the competition and attempted to claim victory by the fact that ZAIA's candidate Homura was the one to rescue Vice President Fukuzoe, Yamashita and Shester. However, Homura instead conceded the victory to Hiden, as without 119nosuke's sacrifice he wouldn't have been able to rescue the hostages. Thus, Gai decided to concede victory to Hiden in exchange for them not talking about Kyogoku's actions, leaving one more round of the competition to go.

For the fifth and final round of the Workplace Competition, Hiden and ZAIA had to put forth representatives to compete to sway the public's opinion in a referendum on whether to rebuild Daybreak Town into an autonomous city populated by HumaGears. ZAIA's candidate was anti-HumaGear politician Masamitsu Yudo while Hiden's was their rapper HumaGear MC Check it Out. At first the competition seemed to be going in Hiden's favor. Yudo gave a speech to a crowd of people filled with ZAIA plants that made it seem like Yudo had lots of it support, but MC Check It Out's music video expressing peaceful coexistence between humans and HumaGears proved popular with the youth. Later on, Aruto and Check It Out exposed and caught footage of Yudo taking bribes from ZAIA, which they intended to expose to the public. During a televised debate between Yudo and MC Check It Out, Aruto and Check It Out revealed the footage, but Yudo claimed the footage was doctored and accused Hiden of making a fake HumaGear in his image to frame him. As Check It Out became angry over being framed as a liar by Yudo, Gai pulled out a ZetsumeRiser and secretly handed it to Check It Out, who used it to become a Dodo Magia. Gai then had Yua transform into the Fighting Jackal Raider and battle the Magia to demonstrate the power of Zaia's new product, the RaidRiser. Aruto transformed into Kamen Rider Zero-One and attempted to interfere but Gai became Kamen Rider Thouser and held him off long enough for Yua to destroy MC Check it Out. Gai then declared to the crowd that had gathered that this was proof of ZAIA's superiority.

The referendum on Daybreak Town ended overwhelmingly in ZAIA's favor, with the vast majority of the public voting against rebuilding Daybreak Town. Thus, ZAIA claimed victory in the fifth and final round and thus won the competition 3-to-2, allowing them to go through with fully acquiring Hiden Intelligence. Gai was later approached by Isamu of A.I.M.S. and offered him a place at ZAIA, but Isamu refused and demanded to know what Gai had done to him. Gai then revealed that he had secretly implanted an AI chip that allowed him to transform, which was why he could use the Assault Wolf manufactured by the Ark. When questioned later by Yua about why he told Fuwa about the AI chip they had implanted, Gai proclaimed that it was only a matter of time before Fuwa found it out himself.

After learning that he had been the one to free Horobi, Isamu went to confront Gai again. Gai revealed to Fuwa that the AI chip in his head contained the data of MetsubouJinrai.NET member Naki, and that all this time Isamu had secretly been acting as a sleeper agent for ZAIA by handing out the RaidRisers to ZAIA's candidates in the Workplace Competition. Gai gloated to Fuwa that he and Yua were nothing more than his tools and proceeded to demonstrate this by using the chip to torture Fuwa. Gai then handed Fuwa the Rampage Gatling key and told him to be an obedient tool. However, Fuwa was able to resist the chip's influence and later used the key to transform into Rampage Vulcan to fight off Thouser and Yua.

As CEO of Hiden Intelligence

As the new President of Hiden Intelligence, Gai issued a recall of all HumaGears and offered to give anyone who had bought one a ZAIASpec in exchange. He also reforged A.I.M.S. into an agency to hunt down and dispose of any HumaGears still active and supplied their members with RaidRisers to allow them to become Battle Raiders. With Hiden Intelligence under his control, Gai intended to use his access to Satellite Zea to delete all the HumaGears data, but he soon discovered that Zea had no data on the HumaGears. Gai later confronted Aruto on this, accompanied by two A.I.M.S. soldiers equipped with RaidRisers, only to discover that the data of the HumaGears had been transferred to the Progrise Keys and that, as they were listed as the personal property of Korenosuke Hiden, they technically did not belong to Gai even though he had acquired Hiden. Gai transformed into Thouser as his henchman became Battle Raiders and attempted to scrap Izu and take the keys, but Aruto was granted access by Satellite Zea once more, enabling him to become Zero-One again. After shielding Izu, Aruto assumed Zero-One MetalCluster Hopper and defeated Thouser. After his henchmen were beaten back by Jin and Fuwa, Gai decided to take his leave for the time being and exited the scene.

Hearing that Aruto had opened up a new company to continue selling HumaGears, Gai showed up accompanied by Eida and Ono to shut it down. Transforming into Kamen Rider Thouser, Gai and his two Battle Raider underlings fought Aruto as Zero-One and managed to overpower him. As they prepared to finish off Aruto with a combined attack, Jin Burning Falcon appeared to provide backup to Aruto and forced the three to retreat. Later, after Yua allowed the HumaGear G-Pen to go free instead of terminating him, Gai scolded her in his office for letting the HumaGear escape, asserting to her that she was just his tool as was to do as he ordered. Gai then went to go destroy G-Pen himself, but was defeated by Zero-One MetalCluster once more. As Eida and Ono tried to help their boss up, Gai brushed them aside and angrily declared to Aruto Hiden that he will get his revenge on him before leaving.

When Hiden Manufacturing repaired the fashion model HumaGear Delmo for a runway show, Gai told Yua they must destroy Delmo, as her performing could sway public opinion in favor of HumaGears. Upon hearing from Yua that Isamu Fuwa was now working as security for Aruto's new company, Gai noted that it was an interesting reassignment and that it was time for them to bring him back under their control by reawakening Naki. Gai then sent A.I.M.S. soldiers Shida and Degawa to attack the Hiden Manufacturing building and deactivate Delmo. As the A.I.M.S. soldiers became Invading Horseshoe Crab Raiders and fought against Zero-One, Fuwa came out and attempted to become Rampage Vulcan to assist Zero-One, but before he could Yua swooped in and forced the Assault Wolf key on him, causing Naki to take over and for Fuwa to become Kamen Rider Vulcan Assault Wolf to attack Zero-One. However, Kamen Rider Jin Burning Falcon then appeared and assisted Zero-One in defeating Vulcan Assault Wolf and driving away the A.I.M.S. forces.

Gai and Yua later attacked the runway show where Delmo was set to perform to shut her down before she could go out. Yua became the Fighting Jackal Raider to go after Delmo, pursuing her outside the building. Gai then transformed into Kamen Rider Thouser, but Zero-One showed up to defend Delmo. However, Gai was able to land a damaging blow on Delmo's leg, preventing her from being able to walk properly and making it so she could not perform on the runway. However, Isamu Fuwa then appeared, having had Gai's brainwashing of Naki broken thanks to Jin and Horobi and prepared to face off against Gai. Unfazed, Gai asserted that both Yua and Naki were his tools, but Naki then spoke up and claimed to not be a tool and to have a dream. Fuwa and Naki then became Kamen Rider Rampage Vulcan and drove off Gai's forces.

Determining that Isamu Fuwa had become too much of a hindrance to his plans, Gai decided to "remove him from the board" and ordered Yua to go out and kill him. Yua transformed into the Fighting Jackal Raider and went out to confront him once more, but was once again defeated by Kamen Rider Rampage Vulcan. Deeming Yua to be a failure, Gai sent out A.I.M.S. Battle Raiders Eifuku and Ito to deal with her, but Vulcan fought them off. Later, when Yua failed to apprehend a HumaGear that had been reactivated, the tennis HumaGear Love-chan, Gai showed up accompanied by Eifuku and Ito and told Yua to step aside, confronting Aruto Hiden and Isamu Fuwa. Gai revealed that Fuwa's memories of his junior high school being attacked by HumaGears were fake and that he had programmed the chip in Fuwa's mind to give him with fake memories of HumaGears attacking his middle school in order to cause him to develop a vendetta against HumaGears. However, Yua then spoke up and declared that she could no longer support Gai, stating that while she didn't have a dream she had principles and one of those was that technology was supposed to benefit humans, not control them. Grabbing a ShotRiser, Yua transformed into Kamen Rider Valkyrie once more to take on Gai, who nonchalantly transformed into Kamen Rider Thouser to dispose of her. While Thouser and Valkyrie fought, Aruto became Zero-One to deal with the two Invading Horseshoe Crab Raiders Gai had brought along. Though Yua was the more skilled fighter, Gai was able to gain the advantage by using the chip he implanted in Yua's mind to remotely cause her pain and disturb her focus. However, Fuwa soon joined the fight as Rampage Vulcan and together, he and Yua were able to defeat Gai and knock him out of his transformation. Gai then grabbed a ZAIASpec and put it on so he could use it continue torturing Yua, but Yua punched Gai in the face and knocked the ZAIASpec off, declaring that he should consider this her resignation.

In response to Naki's hacking of ZAIA's ZAIASpecs, Gai announced he would be shutting down MetsubouJinrai.NET once and for all. Gai later led an army of A.I.M.S. Battle Raiders to the MetsubouJinrai.NET base to put an end to MetsubouJinrai.NET, being met by Horobi and an army of Trilobite Magia that went out to confront them. Gai and Horobi both assumed their Kamen Rider forms and fought while their respective armies duked it out with each other. Thouser managed to overpower Horobi and knock him out of his Kamen Rider form, but before he could finish him off Zero-One interfered. Thouser summoned Gigers to deal with Zero-One, only for Naki to show up and, still connected to ZAIA's systems, to hack Gai's Gigers and Battle Raiders and turn them against Gai. Thouser defeated his army of Battle Raiders, but Horobi then assumed his Kamen Rider form and battled Gai, knocking him out of his transformation with his finisher. Gai then retreated with the rest of the A.I.M.S. forces.

Birth of Ark-Zero

With residual MetsubouJinrai.NET code still inhabiting ZAIA's network, Gai chose to make the RaidRiser available for the mass market, allowing ordinary civilians to transform into Invading Horseshoe Crab Raiders. He chose to market the public RaidRiser under Hiden Intelligence's brand and had Jun Fukuzoe film a commercial announcing the ZAIASpec would be available for civilian use, much to Aruto's disgust that ZAIA was selling such a dangerous weapon to civilians. After filming the commercial, Gai instructed Jun to sound more confident, as they would be meeting with their investors soon.

Meeting with Jun Fukuzoe and Sanzo Yamashita, Gai instructed them to deliberately set off the ZAIASpecs to malfunction on the day the RaidRisers would be made available to the public in order to provide an effective demonstration of the RaidRiser's capability. Appalled by this order, Jun and Sanzo would secretly go to Aruto for help on stopping Gai. Gai was later confronted by Naki and Ikazuchi of MetsubouJinrai.NET and demanded they return their Progrise Keys to him as they were now ZAIA's property. Naki transformed into her Kamen Rider form and charged at the untransformed Gai, slicing off his white suit and leaving him in his ZAIA underwear before leaving with Ikazuchi. Gai then contacted A.I.M.S. to announce a raid on MetsubouJinrai.NET's base. Accompanied by two Battle Raiders and a massive army of A.I.M.S. soldiers, Gai transformed into Kamen Rider Thouser and led A.I.M.S. into MetsubouJinrai.NET's territory, where Gai and his army were met by the four MetsubouJinrai.NET officers. Possessing Jin, the Ark assumed its Kamen Rider form and emitted a signal that paralyzed all the ordinary A.I.M.S. soldiers, leaving only Thouser and the two Battle Raiders. Thouser managed to overpower Kamen Riders Horobi, Ikazuchi and Naki, but was unable to stand against the might of the Ark and was brutally beaten. Just as Kamen Rider Zero-One MetalCluster Hopper arrived, Gai and his forces pulled out. Back at Hiden Intelligence, Gai was confronted by Jun, Sanzo and Shesta, who revealed they had gathered evidence on his misdeeds from the numerous complaints filed against him and would be exposing them to their shareholders at the next conference.

However, Gai then locked himself in Hiden Intelligence's main development room and began deleting all of the evidence from the servers so Jun and Shester wouldn't be able to use them against him. Gai then ordered Satellite Zea to begin mass producing the RaidRisers only to find Zea would not go through with the order. As Gai continued to attempt to get Zea to follow through with the order, Aruto, Jun and Izu arrived in the laboratory through a secret entrance. Aruto revealed that Zea was refusing Gai of its own free will and that all of the RaidRiser preorders had been canceled. Furious, Gai transformed into Kamen Rider Thouser and attempted to attack Aruto and the others. As Izu brought Jun away to safety, Aruto transformed into Kamen Rider Zero-One MetalCluster Hopper and fought Gai, defeating him and knocking him out of his transformation. Shester then stated that they would be forwarding evidence of Gai's wrongdoings to ZAIA. As Jun asked Aruto to return to being CEO, Gai got up and ran back to the CEO desk, refusing to give it up. However, Aruto stated he was too preoccupied with his own business venture to act as CEO right now. After Aruto and the others left, Gai was left alone with Ai, an artificial intelligence developed by Aruto at his new company. Ai asked Gai if he wanted to be friends, but Gai proclaimed he had no need for friends. After being prodded by Ai however, Gai confessed that he was once "friends" with a robot dog he owned that was developed by Hiden Intelligence, but that his father made him put the dog away after he didn't get a perfect score on a test. Ai then sent a signal to Zea, who built a new robot dog for Gai from the data of the original model that was produced. Later, as Aruto was overwhelmed in his face-off against Ark-Zero, Thouser suddenly appeared and blocked Ark-Zero from finishing Aruto off with his Thousand Jacker.

As Aruto got back up and transformed into Kamen Rider Zero-One Metalcluster Hopper again, Ark-Zero engaged both him and Thouser. During the fight, Thouser attempted to strike Ark-Zero with the Thousand Jacker but Ark-Zero grabbed the Jacker and absorbed the powers Gai had copied from it. Despite this, both Zero-One and Thouser were able to overwhelm Ark-Zero with their combined power and force the Ark out of Jin's body. The Ark then bid the two farewell and said they would meet again before vanishing and returning to Daybreak Town. After saving Aruto, Gai returned with him back to the Hiden Manufacturing building and apologized for how he acted, but Aruto stated that Gai would have to do a lot more than that to atone for what he did. Gai later visited Fuwa and Yua and apologized to them, as well as A.I.M.S. While Yua was still incredibly distrustful of Gai, Fuwa simply asked that Gai let A.I.M.S. become independent of ZAIA.

After Izu requested that Gai have Hiden Intelligence begin producing HumaGears to help with the destruction the Ark was causing, Gai held a conference with Hiden's Board of Directors where he announced he was stepping down and ceding the position of President back to Aruto Hiden.

Following the Ark's destruction, Williamson Yotagaki arrived from ZAIA Enterprise's main branch to relieve Gai of his position as CEO of ZAIA Japan, citing his responsibility in the Ark crisis and failure to control it as his reason for doing so. Yotagaki stated that he would be taking Gai's place as CEO and transferring him to a new division of ZAIA Japan, the "Thouser Department", where he would work as Kamen Rider Thouser to take out threats to ZAIA.



           Kamen rider zero one logo.png Villains

Ark | Horobi | Naki | Jin | Ikazuchi | Little Assassin | Azu | Kamen Rider Ark-One
Magia: Berotha Magia | Kuehne Magia | Ekal Magia | Neohi Magia | Onycho Magia | Vicarya Magia | Gaeru Magia | Mammoth Magia | Dodo Magia | Arsino Magia | Trilobite Magia | Dodo Magia Chick

ZAIA Enterprise
Gai Amatsu | Giger
A.I.M.S.: Yua Yaiba | Eida | Ono | Degawa | Shida | Eifuku | Ito
Raiders: Crushing Buffalo Raider | Splashing Whale Raider | Dynamiting Lion Raider | Storming Penguin Raider | Scouting Panda Raider | Battle Raiders

Es | Bell | Moore | Luga | Bugo | Kamen Rider Abaddon

Alternate Timeline
Finis | Will | Soreo Hiden

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