Gai, also called Guy, is Riki's former pairing partner and second-in-command of the Bison gang in Ceres. Their deep mutual reliance and partnership originated in their shared past as Guardians. Gai consistently displays a calm, reasonable, and collected nature, serving as a stabilizing counterbalance to Riki's fiery impulsiveness. This dynamic made them inseparable within the slums, with Gai providing essential emotional and strategic support during Riki's leadership of Bison.

When Riki vanishes mysteriously for three years, Gai assumes leadership of Bison. He respects Riki's privacy upon his return, avoiding questions about his absence due to his commitment to their bond and desire to rebuild their relationship. However, after learning Riki had been forcibly kept as Iason Mink's pet during those years, Gai resolves to rescue him. His determination intensifies upon realizing Riki's enslavement was forced, fueling a plan to retrieve him from Tanagura at any cost.

Gai's emotional stability fractures as jealousy and possessiveness consume him. His inability to accept Riki's connection to Iason drives extreme actions, including kidnapping Riki and attempting to sever the pet ring binding him to Iason. Misinterpreting Riki’s loyalty to Iason as solely coerced—and refusing to acknowledge Riki’s complex emotional ties—Gai escalates their conflict. In a climactic confrontation, he cuts off Riki’s penis in a misguided effort to "free" him. This triggers Iason’s retaliatory mutilation: Gai loses his left arm and suffers genital mutilation.

The physical collapse of their surroundings during this confrontation kills Riki and Iason, while Gai survives. Left physically broken and emotionally devastated, Gai grapples with profound guilt and despair over his role in Riki’s death. His final state is irreversible isolation, marked by the loss of his relationship, autonomy, and purpose. This conclusion underscores his tragic arc from devoted partner to agent of destruction, shaped by obsessive love and fatal miscommunication.