Kyou Yahagi debuts as an elite fighter in Team Asteroid (AL4/Foo Fighters) under Ren Suzugamori. Highly arrogant, he frequently styles himself "The Great Kyou" and covets the team leadership, believing his skills superior and displaying open resentment towards Ren. He initially wields a Spike Brothers deck built for aggression, leveraging units like Sky Diver, General Seifried, and later Demonic Lord, Dudley Emperor to superior call units and unleash multiple attacks per turn. Defeat by Kai Toshiki in the national tournament results in his expulsion from Foo Fighters for weakness. This loss shatters his confidence, triggering instability and an obsession with revenge against both Kai and Ren. He forms Team Avengers with other exiled members to disrupt the Vanguard circuit and prove his strength. Targeting Kai during a regional tournament, he is instead defeated by Aichi Sendou; Aichi's PSY Qualia and strategy centered on "Young Pegasus Knight" expose Kyou's tendency to panic under pressure and fixate on eliminating threats rather than securing victory. His revenge quest continues. In the Asia Circuit, he orchestrates "Project Yeti," disguising himself to lure strong fighters and steal their VF Circuit invitations. He battles Kai again using an updated Spike Brothers deck featuring Dudley Emperor's Limit Break, losing despite ignoring an avalanche threat to finish the fight. Though Kai rescues him, Kyou vows future retaliation. Later, after jungle training, he temporarily adopts a Megacolony deck with Martial Arts Mutant, Master Beetle to counter Leon Soryu's Aqua Force, but fails to secure Leon's Circuit spot. He then ambushes Team Unknown, losing to Joker X (Tetsu). During the Link Joker crisis, he and Team Avengers encounter Ren battling Reversed fighters. They intervene, fighting the Reversed students and later aiding Team Asteroid at the Tatsunagi building against Reverse forces. By Season 4, his vendetta against Ren persists through petty acts like sending a mocking Jack-in-the-box to Ren's graduation party. In Vanguard G Season 2, he rejoins Team Asteroid for the United Sanctuary Branch G Quest, battling Team TRY3. Manga portrayals diverge. Here, he initially takes over Kamui Katsuragi's card shop, intimidating customers with fight gloves. After losing to Aichi, he develops grudging respect, becoming a more sympathetic figure driven by an inferiority complex and desire to prove himself. He allies with Aichi against other Foo Fighter bosses and temporarily gains PSY Qualia, becoming a "PSY Qualia Zombie" during the Link Joker arc. His manga deck is Nubatama (later adapted to Murakumo in the TCG), employing lockdown tactics with units like Dueling Dragon ZANBAKU and Left/Right Arrestors to prevent opponents from standing their vanguard or riding grade 3 units. Kyou is characterized by his flamboyant appearance—white hair, purple eyes, and flashy outfits—earning fan nicknames like "Flashdance Kyou." Persistent resentment toward Ren and Kai underscores his actions, though his later involvement combating larger threats indicates a shift from pure antagonism to reluctant cooperation. His birthday is July 4.