Momokichi Momoi commands the criminal underworld as a powerful mob boss and owns the professional baseball team the Peach Twisters. He enforces brutal management tactics, executing underperforming players in a pattern echoing past killings dubbed "The Bloody Pennant Race." His empire includes the Peach Bowl bowling alley, where he regularly competes against challengers like his daughter Momomi Momoi, intertwining family dynamics with his illicit operations.

His feared reputation and deep underworld connections make him a kidnapping target. The Danger Service Agency (DSA) orchestrates an abduction at the Peach Bowl on orders from Hiroka, his head of security. When bodyguards intervene, chaos erupts. Momokichi dies from an unintended head injury sustained during the struggle, striking a ventilation pipe.

His death sparks immediate vengeance from Momomi, who hunts those responsible and executes the bodyguards for their failure. His legacy endures through naming themes: "Momo" (peach) appears in his name, his daughter's, and properties like the Peach Twisters and Peach Bowl. Familial ties reveal deeper complexity—Momomi is his confirmed daughter, while DSA member Mikura Suzuki is established in related media as his illegitimate child, making her Momomi’s half-sister.

Momokichi’s demise drives the sequel *Mezzo DSA*, where Momomi’s death and unresolved family vendettas fuel subplots. Sakura Sakurada, Momomi’s lover, pursues revenge against Mikura after uncovering their blood relation.