In the neon-soaked back alleys of Shinjuku's Kabukicho district, a fifteen-year-old boy named Kenichi is consumed by a single purpose: to avenge his father's murder. His path crosses with Maba, a fifteen-year-old girl who is a seasoned killer. Maba bears a prosthetic right hand and left leg, the remnants of a past tied to a shadowy organization she once served. Now she is hunting the person who killed her former boss. Recognizing a shared enemy and a mutual need for strength, Kenichi and Maba forge a "revenge contract" — he will help her hunt her target, and she will help him kill his father's killer. The arrangement quickly deepens into a reluctant but intense partnership as they begin living together in the chaotic heart of Kabukicho.

The two teenagers must navigate a world of ruthless yakuza, underground gambling dens, and violent power struggles. Their bond is tested by the arrival of other dangerous residents of the district, each with their own agendas. Maba's combat skills and Kenichi's raw determination make them a formidable pair, but every step forward invites new threats. The story captures their defiant struggle to survive in an environment that offers no mercy, driven by the tagline: "Even so, we will live on, flipping the middle finger to the world." As they carve out a place for themselves, the lines between revenge, survival, and loyalty blur, forcing both to confront what they are willing to sacrifice. At its core, this is a raw, transient tale of two outcasts bound by necessity, trying to find meaning and a future in a place where both are constantly in doubt.