Koiko, the young wife of Sabu from the Menso yakuza group, carves out a domestic routine in their modest apartment, balancing household duties like cooking and cleaning with moments of tenderness toward her husband. Initially sheltered from the harsh truths of yakuza life, her naivety fractures when her desperate intervention to save Sabu’s life inadvertently captures the interest of his superior, Tominaga. The latter’s growing obsession with her sparks manipulation of Sabu’s loyalties, entangling Koiko in escalating gang rivalries.

Her unwitting aid to the aging Menso leader deepens her involvement, heightening tensions with rival factions and exposing her to peril. Defined by empathy and fervor, her personality aligns with ketsueki-gata principles—her blood type B linked to unpredictability and subtle self-interest. Yet these traits fuel her resilience as she confronts external threats and internal power shifts, adapting to survive.

The narrative interweaves humor and tension, tracing her awakening to the dangers of Sabu’s world. Rather than recede into passivity, she maneuvers challenges with agency, her growth left open-ended by the OVA’s adaptation of its source manga.