Based on the romance manga *Koiko no Mainichi* by George Akiyama, the story follows Shinjuku gangster Sabu and his young wife Koiko as they try to maintain a normal life amid the constant interference of gang politics and criminal deals. After Koiko saves Sabu’s life, his gang boss Tominaga becomes infatuated with her. Determined to separate the couple, Tominaga sends Sabu into increasingly perilous situations, hoping to provoke his arrest. Once Sabu is incarcerated, Tominaga attempts to compel Sabu to “take care” of Koiko while he is in prison.