Mio Shizunaga is a high school student leading a double life. Although he is the son of a yakuza manager, he has managed to live as an ordinary young man, keeping his family background a secret. His attempt at a normal existence is shattered when his father, the organization's director, is shot and seriously wounded by a rival faction. With his patriarch incapacitated, Mio is suddenly thrust into the underworld as the acting leader, a role he reluctantly accepts out of admiration for his father.

Navigating this dangerous new reality, Mio is not entirely alone. By his side is Shinjin Oga, a stoic and fiercely capable bodyguard who serves as both his caretaker and his secretary. Oga harbors a deep, possessive devotion to Mio that goes beyond professional duty, creating a complex dynamic of dependency and protection. As Mio struggles to command respect from subordinates who openly challenge the new acting leader, he begins to witness the brutal truth of the back society his father once navigated. Together, this pair of black sheep must resist a fate written by violence and conspiracy, uncovering the truth behind the mysterious incident that changed their lives forever. The story unfolds in a modern Japanese setting where the line between the ordinary world and the violent realm of organized crime blurs, leading Mio from the classroom to the heart of a yakuza power struggle.