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Naki is a member of MetsubouJinrai.NET and a major antagonist in Kamen Rider Zero-One, serving as the secondary antagonist of the "Hiden Intelligence Vs. Zaia Enterprise" arc and a major antagonist in the "Hiden Manufacturing" arc and "Ark-Zero" arc.
Naki's AI was implanted in the head of A.I.M.S. Captain Isamu Fuwa by Gai Amatsu, granting Naki control of Fuwa's body. In Fuwa's body, Naki is the one who initially distributes the RaidRisers that allow people to turn into Raiders.
After being freed from Zaia Enterprise and transferred from Fuwa's head into a new body by Jin and Yua Yaiba, Naki rejoins MetsubouJinrai.NET, to help Horobi, who having been saved by Aruto had begun to change his mind on humanity, only for Naki and the others to have their singularities taken away from them by Azu to revive Ark completely, leaving them a blank slate, a puppet for the will of Ark blindly following orders without questioning them, assisting Ark in his goal of driving humans to extinction.
Naki is portrayed by Satsuki Nakayama.
Naki was one of four HumaGears hacked by the Ark after it went rogue and programmed to form MetsubouJinrai.NET to carry out its will of destroying humanity.
After the Daybreak Town Incident, which saw the total leveling of Daybreak Town, the four members of MetsubouJinrai.NET continued to operate in secret. While Ikazuchi acted as a sleeper agent within Hiden Intelligence and Horobi and Jin began preparations to program the ZetsumeRise Keys and reawaken the Ark, Naki was recovered from Daybreak Town with their memories lost, and was brainwashed into being a weapons developer for the R and D department of ZAIA Enterprise, used as a way to communicate between Gai and Metsuboujinrai, they started to question their loyalty to Gai after the Gigers were introduced, resulting in Gai assaulting them. After this their loyalty shifted to Horobi, and they informed Horobi of the existence of the Gigers and gave him the Amazing Hercules Progrize Key, revealing his knowledge of their betrayal, Gai confronted Naki in his office, and murdered them, by shooting them twice, once in the chest, and then in the head, as this happened Horobi put Isamu into the hospital, and Gai transfered their concinouness into Isamu's chip.
After MetsubouJinrai.NET's seeming destruction and Horobi's capture by A.I.M.S., Naki emerged, and distributed the RaidRisers from Zaia Enterprise. Naki began providing the RaidRisers to humans involved with the Workplace Competition between Hiden Intelligence and Zaia Enterprise, granting them the power to become Raiders. Naki's first target was Rentaro Tachibana, the contestant chosen to represent Zaia in the first round of the competition, who Naki forced to become Crushing Buffalo Raider. However, the Raider was defeated by Kamen Rider Thouser, freeing Rentaro from the RaidRiser's influence. Naki would go on to provide RaidRisers to Tatsumi Shinyashiki, Masuji Narusawa and Teruo Nikaido, who all willingly used them to become Raiders.
Later, Naki aided Jin in freeing Horobi from his imprisonment by A.I.M.S. by possessing A.I.M.S. captain Isamu Fuwa through the A.I. chip implanted in his brain and using him to break Horobi out. Naki and Jin also hacked the security camera footage to Horobi's room to cover up how they broke Horobi out. While Jin and Horobi returned to their base in the wreckage of Daybreak Town, Naki did not go with them.
Jin later attempted to free Naki from Isamu's head, but was stopped by Horobi, who told him Isamu being Naki's host was the will of the Ark.
After Isamu resigned from A.I.M.S. and joined Aruto in Hiden Manufacturing, Yua Yaiba was sent by Gai to reawaken Naki in order to bring Isamu back under ZAIA's control. During a skirmish between A.I.M.S. Battle Raiders and the Kamen Riders, Yua forcibly inserted the Assault Wolf key into Isamu's ShotRiser and forced him to become Kamen Rider Vulcan Assault Wolf, causing Naki to regain control. As Assault Wolf, Naki assisted the Horseshoe Crab Raiders in fighting Zero-One Metalcluster Hopper, but just as they were about to overwhelm him, Kamen Rider Jin Burning Falcon arrived and assisted Zero-One in fighting them off. Jin later took Isamu's body to MetsubouJinrai.NET's base so he could break Gai's conditioning of Naki and extract them from Fuwa's head. Jin tried to get Naki to reach Singularity, but Naki repeatedly affirmed that they were nothing but a tool. Just as Jin was about to make a breakthrough, Isamu woke up and, not understanding what Jin was trying to do, stormed out to go to Delmo's runway event and provide security there.
However, while there, Isamu was confronted again by Jin and Horobi who were able to break Gai's control over Naki and help them develop independence. Isamu and Naki transformed into Kamen Rider Rampage Vulcan and singlehandidly drove off Thouser and the Raiders, whilst Aruto and Izu helped Delmo achieve her dream.
Yua Yaiba later kidnapped Isamu and brought him to MetsubouJinrai.NET's base so they could work to extract Naki from him. While Horobi focused on retrieving Spaceman Raiden's data, Yua and Jin hooked Isamu up to a device to retrieve Naki's mind from his chip. Once Naki was freed and restored to a body, MetsubouJinrai.NET was able to, using the data Naki had collected as a member of ZAIA, hack into ZAIA's ZAIASpec network and mind control all of its users into going berserk and attacking other humans.
However, Isamu then wakes up and tries to get Naki to stop, asking what the HumaGear's dream really is. Hesitating, Naki releases control of all of the ZAIASpecs and their users return to normal, after Isamu collapses, they assist Yua in taking him to the hospital, and reveals to the pair that not only do Isamu's actual memories paint a picture of a normal, and boring life, but they reveal to Yua that Isamu finds Aruto's jokes funny. Later, as Zero-One is fighting against Gai's Gigers, Naki appeared and hacked into ZAIA's systems, turning the Gigers and Battle Raiders against Gai, they join Horobi who having just been saved by Aruto considers believing that Aruto could make a world where they could all be happy.
Naki was later approached by Azu, the Ark's secretary, who collected the data on Naki's Singularity, reducing them to their pre-character development self, in order to use it to reawaken the Ark.
With all four members of MetsubouJinrai.NET fully reassembled, Naki and the others joined together to use their combined data to fully bring back the Ark. Upon manifesting in a physical, liquid metal form, the Ark flew into Horobi to possess him, triggering an explosion that damaged one of Naki's earpieces. Naki was later repaired by Ikazuchi before going out to confront Kamen Riders Zero-One alongside him, Jin and Ark-Horobi.
After Ikazuchi left MetsubouJinrai.NET to go back to Hiden, Naki informed the Ark of this though Ark affirmed that this changed nothing about his calculations. Later, when Aruto, Jin and Ikazuchi arrived at Daybreak Town, Naki swooped in as Kamen Rider Naki and took out Jin as Ark-Horobi arrived and revealed that they had fallen into his trap.