Rescued from homelessness by veteran devil chojin Sunshine, who recognized his potential, Check Mate endured rigorous training designed to eliminate his capacity for pain and erase concepts like failure or defeat. Unofficially adopted by Sunshine, acting as both father figure and coach, he achieved imperviousness to physical pain while remaining susceptible to injury. He gained the ability to transform by pressing buttons on his chess-piece shoulder pads, shifting between rook and knight forms.

Initially positioned as an antagonist seeking revenge against the New Generation chojin for Sunshine, Check Mate first confronted Mantaro Kinniku. Exploiting his pain immunity, he dislocated joints to escape holds and dominated much of the fight. His lack of empathy surfaced when he turned against Sunshine's protests and attempted to murder Mantaro, even attacking Sunshine as he saved a child, drawing crowd disapproval he ignored. Mantaro exploited accumulated damage to his knee, securing victory with the Kinniku Buster. Sunshine carried the injured Check Mate away, vowing to retrain him for strength and justice.

This defeat catalyzed significant development, transitioning Check Mate into a supporting ally for Mantaro and the Justice Chojin. Reappearing later, he initially intimidated Mantaro but then defended him from an illegal attack by Fork the Giant, citing fair play. He explicitly stated his loss to Mantaro changed his worldview, prioritizing honorable combat over hatred or victory. He accompanied Mantaro to subsequent matches, observed battles alongside him, participated in group activities like karaoke, and demonstrated protective instincts by saving Mince from Bone Cold's assassination attempt.

His growth continued as he prioritized the safety of his unfit partner, Shinya, over victory during a tournament. Evading Mr. Gacha in knight-form inadvertently injured Shinya further, prompting Check Mate to cut their binding ties, accept disqualification, and carry Shinya to safety, showcasing newfound compassion and selflessness.

He later joined allies consoling Mantaro after a loss, supported training efforts like helping Kevin Mask prepare alongside Jade, and attended significant matches as a spectator.

During a perilous mission to save Robin Mask, Check Mate trained with Ilioukhine before disruptions. He helped build a time-ship, volunteered for the mission, contributed his "Stallion Honourable Driver" to the construction, and managed the air-conditioning unit. He aided in saving Robin Mask but faced suspicion after an ally's injury. When a tournament was announced to resolve conflict, he pleaded unsuccessfully with Seiuchin to be his tag partner. Following Seiuchin and Neptuneman, he witnessed Seiuchin's beastly transformation and overheard talk of the "Perfect Chojin Revival." He attacked Neptuneman but was brutally defeated by a "Cross Bomber" that removed the skin from his face. Found unconscious, he was displayed in a coffin during the tournament's opening ceremony. Severely weakened, he managed to warn the New Generation about Seiuchin's transformation before paramedics took him away. A recent ambiguous sighting described a shadowy figure with similar boots and cape boarding a bus heading towards the tournament.

In a later confrontation within d.M.p headquarters, Check Mate re-emerged as the third opponent Mantaro and Terry the Kid faced to rescue Meat Alexandria. He battled Mantaro in a chessboard-themed ring, utilizing his rook form to nullify attacks and his knight form to execute techniques like the "Honorable Stallion Driver."