Fujio Saitō, known as Saru, shares a contentious past with Makoto rooted in an unpaid debt from their eighth-grade years—a lingering grudge he refuses to release. His sharp, short black hair and brown eyes complement a striking wardrobe choice: a black button-up shirt worn deliberately over a crisp white undershirt.

Driven by ambitions to shed his self-perceived fragility, he enlisted in a local Yakuza family, earning the responsibility to protect the boss’s daughter. A critical error during this duty forced the Yakuza to recruit Makoto’s aid, culminating in Saru’s ritualistic pinky severance as punishment. Yet he persists as a recurring fixture in Makoto’s endeavors, bridging the protagonist’s world with Ikebukuro’s shadowy underbelly through his underworld connections.

Beneath a veneer of grudging cooperation simmers an unyielding bitterness toward Makoto’s unresolved debt, a resentment that fuels his capacity to nurture grievances across years. This duality—a pragmatic allyship entangled with vindictive pride—defines his fractured loyalty, shaped equally by his Yakuza entrenchment and the unresolved tensions of their shared history.