Tatsuya Yamazaki began his journey alongside Senda Naoki, shadowing Sugata Kazushi to infiltrate the Front of Armament (T.F.O.A.). While navigating middle school, the pair forged a pivotal bond with Bandou Hideto, prompting all three to enroll at Kurosaki Industrial. Following Sugata’s death and disillusioned by T.F.O.A.’s new leadership under Kunou Hideomi, Bandou defected to Suzuran High School, intent on building a rival faction to challenge the organization. Yamazaki and Senda joined him, solidifying the Bandou Faction’s rebellion.

Their rise collided with Suzuran’s established hierarchy, sparking friction with the Ebizuka Trio. Tensions erupted when Yamazaki ambushed Yasu, an ally of transfer student Harumichi Bouya, hurling a steel pipe from a bridge. This violent escalation provoked Bouya to crush the faction, culminating in Yamazaki’s humiliating defeat.

Fleeing T.F.O.A.’s retaliation after Senda’s assault, Yamazaki betrayed Bandou by exposing his location to the organization. The trap, sprung by Mito Yasuyuki, left Bandou battered—a betrayal that backfired when T.F.O.A. later turned on Yamazaki himself, shattering his resolve.

Desperate for redemption, Yamazaki targeted Kunou Hideomi in a reckless motorcycle assault, seeking reconciliation with Bandou. The stunt underscored his spiraling desperation but failed to salvage alliances. Yamazaki abandoned Suzuran before graduation, exiting the conflict’s frontlines.

His combat failures—crushed by Bouya and outmatched by Mito Yasuyuki—sealed his faction’s collapse and reputation’s ruin. These defeats accelerated his descent into moral ambiguity, leaving him isolated from former comrades and trapped in a cycle of fractured loyalty and unrealized atonement.