Shingo is initially shown to have an inflated and pretentious ego as a "Perfect Duelist", being selfish, vain, pompous, and incredibly egotistical similar to Chazz Princeton from the Yu-Gi-Oh! GX Series. As such he enjoys being praised by his crew and showing off in front of everyone, although he doesn't take kindly to anyone who interrupts him. His defeat at Yuya's hands caused him to develop a grudge against him, but also caused him to develop some of his mannerisms. Shingo also often makes gestures relating to darts when he feels they suit the situation.
He shows a degree of cunning, pretending to be friends with Yuya in order to steal his "Timegazer Magician" and "Stargazer Magician. After he managed to steal them, he then imprisoned Yuya's friends to force him into a Duel. Throughout the Duel, he continuously mentioned how he was now the chosen one, able to Pendulum Summon. Shingo is also shown to be extremely materialistic and acquisitive, valuing only rare cards. This is shown in his Decks which are initially comprised of only Parallel Rare cards. Furthermore he seems to be quite shallow with cards, judging them solely for their ATK or DEF values and their Level regardless of what effect they may have.
Despite this, not only did he develop some of Yuya's mannerisms after his first defeat at his hands, but during their second Duel, he also developed a similar attitude and Dueling style, enjoying entertaining the crowd and encouraging Yuya to do the same. He accepted his second loss to Yuya gracefully and told him that he'd Duel him any time he wanted. He later showed sincere sympathy for Yuya when he was depressed after Yuzu's disappearance.
Shingo was contacted by Declan to obtain Yuya Sakaki's Pendulum Monsters, no matter the means, while he threw darts at a picture of Yuya.
After class one day, he approached Yuya and his friends, throwing three sucker-tipped darts at Yuya before introducing himself, stating that he was a fan of Yuya and his Pendulum Summoning. Yuya was going to show his friends a Pendulum Summon at his own Duel School, but Shingo offered the use of the Center Duel Field at Leo Duel School. Yuzu Hiragi wasn't happy about it, but Yuya's other friends all agreed, and Shingo showed them around the school before he took them to the Duel Field. There Yuya and his friends were met by Shingo's crew of friends: Ootomo, Yamabe, and Kakimoto. Shingo asked to show his crew Yuya's Pendulum Monsters, and Yuya reluctantly showed him his "Stargazer Magician" and "Timegazer Magician." Shingo promptly swiped them and showed them to his crew, before announcing his intention to keep them. He offered Yuya the chance to Duel to get them back, much to the anger of Nakajima, who was monitoring Shingo for Declan. Declan allowed Shingo to Duel Yuya. Shingo tossed Yuya some of his Common cards to replace his Magicians, calling them trash cards. To ensure that Yuya would Duel, Shingo had Yuya's friends placed on top of one of the bridges in "Dark Town's Prison Tower," furthermore endangering them with the prospect of their perch being damaged by Action Trap Cards. On the first turn, Shingo drew "Timegazer Magician," but was instructed to retain it in his hand by Declan. Instead, he Summoned "Lightning Board" and pursued Yuya, destroying his "Performapal Whip Snake" after it was weakened by Action Trap Cards. Yuya continued to play defensively, but to no avail; on Shingo's next turn he drew a card that allowed him to add "Stargazer Magician" to his hand and he proceeded to Pendulum Summon his "Darts Shooter" monsters with Declan's assistance. Shingo was amazed at the Summon, declaring himself a chosen one.
He put Yuya on the ropes with his "Darts Shooter" monsters, though Yuya proceeded to create an attack lock with the card he'd taken from Shingo - "Block Spider." Shingo nullified the lock on his next turn by negating the effects of his Pendulum Monsters. In response, Yuya increased the DEF of "Block Spider" to the point that only Shingo's "Ultimate Darts Shooter" was able to land a hit. Yuya then reclaimed his Pendulum Monsters with "Empty Fishing" since their effects had been negated and proceeded to Pendulum Summon the next turn himself, using his Pendulum Monsters to allow "Odd-Eyes Pendulum Dragon" to destroy all of Shingo's monsters, while Shingo frantically tried to dodge the shockwaves. Yuya then finished Shingo off with Shingo's own "trash card," "Block Spider." Despite his loss, Shingo ordered his crew to take the Pendulum Monsters by force, but Sora Shiun'in knocked out Shingo's friends, then Shingo himself out with his lollipop stick.
After his defeat, he acquired new cards that he tested out against one of his crew. They praised him, calling the cards strong, but Shingo corrected them, claiming that it was him that was strong, and stating that he had all the qualities of a "Perfect Duelist." After using a few expressions similar to those that Yuya had used, his friends wondered if Yuya had rubbed off on Shingo, but he denied it and vowed he would crush Yuya. He was later hanging out with his crew in an abandoned warehouse, waiting for his favorite food, and chastised his friends who had brought it to him, for being late. As he was eating, Yuzu, who had overheard Shingo's crew talking about Shingo's wish to defeat Yuya, arrived, surprising him to the point that he choked on his food. Yuzu demanded that he Duel her, continuously denying his attempts to speak. When he protested about this, she angrily called him a coward and a second-rate Duelist, infuriating Shingo. Yuzu continued to insult Shingo, and he furiously agreed to the Duel. Before they could, the door to the warehouse opened, revealing a mysterious masked figure, who activated a strange Duel Disk. Shingo Dueled him instead, mockingly dubbing him "Knight-kun" for coming to Yuzu's rescue. "Knight" placed his entire hand face-down on his first turn, and Shingo seized his chance to bring out "Mobius the Frost Monarch", then Tribute it to Summon "Mobius the Mega Monarch," destroying all five of "Knight's" Spell Card's.
Despite this, "Knight" activated his three "The Phantom Knights of Shadow Veil" Spell Cards from the "Graveyard," Special Summoning them as monsters to defend against Shingo's attack. On his next turn, "Knight" used the remaining cards to Xyz Summon, to the surprise of Shingo, "Dark Rebellion Xyz Dragon." The two exchanged insults about how the other failed to live up to their expectations, before "Knight" used his Xyz Monster's effect to halve the ATK of "Mobius" twice, adding the stolen ATK to "Dark Rebellion" in addition, and reduced Shingo to 100 Life Points with a single attack. The force of the impact sent him flying, despite the match not being an Action Duel. "Knight" questioned Shingo about LDS's connection to Academia, holding up an LDS badge. Shingo replied that the badge was worn by all LDS students and that he knew nothing of Academia. "Knight" turned to leave, but Shingo refused, pointing out that a Duel was still on. He played "Ice Rage Shot" in an attempt to defeat "Knight," but "Knight" negated the Trap using "Phantom Des Spear" and inflicted enough damage to win without even turning his back. The spear pierced Shingo's jacket, pinning him to the wall in shock. "Knight" then removed his mask to reveal that he resembled Yuya to the point that Shingo and his friends believed that he was Yuya. Shingo passed out from the stress of the Duel and his crew carried him away in fear.
Shingo exaggerated his injuries and was subsequently hospitalized. Mr. Sawatari vowed revenge on Yuya, and was deciding on legal action, but they were visited by Henrietta, who instead suggested she let them handle it, to prevent Mr. Sawatari from attracting attention during the upcoming election. Shingo's crew later accused Yuya of attacking Sawatari, claiming that their friend was in great pain - in reality, Shingo was happily chowing down on melons in bed. He was later discharged from hospital, and he approached Yuya and Yuzu, offering Yuzu his handkerchief and telling Yuya that he shouldn't eat so messily in front of a lady. He joked that he'd heard that Yuya had attacked someone else, but he knew Yuya wasn't responsible, believing him incapable of defeating Professor Marco, even with Yuya's "cowardly" Pendulum Summoning (a fact that he hadn't told his father, given that they hadn't seen each other since Shingo had been discharged). He justified this statement by pointing out that only Yuya had them (not knowing that Declan also had Pendulum Cards), and commented that LDS was attempting to mass-produce Pendulum Monsters, which he would obtain to get his revenge. He told Yuya that he'd see him at the Junior Youth Championship and then casually walked away, as that was all he'd come to say.
At the Championship, he accompanied the Course representatives and Shun. His first Duel was to be against Yuya the next day. Shingo entered the arena the next day dressed in homage to Mabuta no Haha, proclaiming himself the world's greatest Duelist, and calling himself "Neo New Sawatari." Shingo claimed that Pendulum Summoning would be Yuya's downfall, and pointed out his (unfounded and quickly disproven) grudges against Yuya. They began their Duel, with Shingo unveiling his new "Yosenju" monsters and adding cards to his hand. Yuya Pendulum Summoned next turn and fought back, but Shingo used his "Yosenju" cards to deny him Action Cards and add "Yosenju" Pendulum Monsters from his Deck to his hand and Pendulum Summoned "Mayosenju Daibak." He then activated his "Yosen Realm Whirlwind" to send the cards bounced to Yuya's hand back to his Deck instead, and cleared his field when the self-returning effects of his "Yosenju" monsters triggered his "Yosen Tornado," returning the cards to Yuya's hand and thus to his Deck. Despite his pinch, Yuya simply laughed and Set his remaining cards, and then turned to find more Action Cards. Shingo brought out his "Yosenju" legion of monsters again the next turn and wiped Yuya's field clean, but this triggered the effect of Yuya's "Nameless" card, which caused Shingo's own monsters to become subject to his deadly combo. Shingo was impressed, but attempted to end the Duel that turn anyway. Yuya was able to use a "Great Escape" Action Card to end the Battle Phase, leaving Shingo's field and hand almost bare. Admitting that he was enjoying the Duel, when Yuya didn't Pendulum Summon the next turn and the crowd chanted for it, Shingo delivered, Pendulum Summoning two "Yosenju" and using them as Tributes to Summon "Daibak." Yuya was able to reduce his damage, and after the crowd began cheering for a Pendulum Summon again, Shingo encouraged Yuya to live up to their expectations, keeping "Daibak" on the field since he'd Tribute Summoned it. Yuya was able to replenish his hand and bring out "Odd-Eyes," again, then damage Shingo, who kept "Daibak" on the field by destroying "Yosenju Shinchu L." Much to Shingo's shock, Yuya Fusion Summoned during the Battle Phase and brought out "Beast-Eyes Pendulum Dragon," which also had 3000 ATK, and both Shingo and Yuya leapt for Action Cards. Shingo attempted to inflict damage to Yuya since his monster had been destroyed, but Yuya had gotten "Miracle," which had prevented his monster's destruction, allowing the effect of "Beast-Eyes" to go through and wipe Shingo out. Though he refused Yuya's hand up, Shingo took the loss gracefully, offering to Duel Yuya any time, and both of them waved to the cheering crowd.
During the Battle Royal, after the video feed for all of the areas was cut, Shingo took advantage of his father's influence to barge into Declan's control room and ask what was going on, as he wanted to see how far in the tournament Yuya would get. Declan allowed him to stay and offered him a chance to take place in a revival match. Declan explained the situation regarding Selena, Shun and the invading Obelisk Force to Shingo and sent him to assist Selena, Shun and Tsukikage. He arrived in time to use an Action Card to save Tsukikage. He explained why he was here, but was then shocked by the intrusion penalty of 2000 LP, a detail that Declan had not warned him about. Despite this, he claimed that he'd show them why he was "LDS's strongest." Showing off his new "Underworld Troupe" Pendulum Deck, he managed to destroy one of the Obelisk Force's "Ancient Gear Triple Bite Hound Dog's" without triggering their combo, though he inadvertently allowed the Obelisk Force to bring out "Ancient Gear Ultimate Hound Dog" and halve their Life Points. Gong then joined the Duel, using his card effects to transfer Shingo's Pendulum Cards to Shay's hand, which allowed Shay to win the Duel with "Raidraptor - Revolution Falcon". Shingo celebrated jovially, and later saw the climax of Yuya's inconclusive Duel with Sora Shiun'in. After the expiration of the Battle Royal, Shingo commented to Declan that he'd chased out the Academy soldiers as he'd been asked, suggesting that this made him one of the Lancers now. When Gong asked him about them, Shingo explained that the Battle Royal had been a selection exam for the Lancers.
When Yuya asked Declan why they'd been fighting as opposed to the Youth and Pro teams, Shingo explained that the Youth team were wiped out, save Yuu Sakuragi, which was why he'd been sent to help. When Selena revealed herself to be from the Academy, Shingo believed her to be a spy, and questioned her until Tsukikage stepped in to fend him off. Delcan then reassured them that Selena was no spy. During Yuya's Duel with Declan, Shingo filled Dennis in on Declan's Dueling and he expressed sympathy for Yuya's loss of Yuzu.
- Shingo is the first rival that Yuya had a duel with. He's also one of three characters in the series to use Pendulum Summoning.
- Shingo views himself as the "Perfect Duelist" but he has never won any major duel as of yet. Until his Tag Duel in Episode 49 against the Obelisk Force.
- He frequently changes Decks in the sereies. He originally had a "Darts Shooter" Deck, followed by "WATER", then "Yosenju" and currently "Underworld" Deck.