Taro Sakamoto was once a legendary hit man considered the greatest of all time. Bad guys feared him! Assassins revered him! But then one day he quit, got married, and had a baby. He's now living the quiet life as the owner of a neighborhood store, but how long can Sakamoto enjoy his days of retirement before his past catches up to him?!
Sakamoto is concerned about the safety of his family and friends. How will he protect them and his life as a civilian? Meanwhile, Takamura's personality goes out of control, turning X into a killing machine. In the midst of the chaos, Rion's personality appears and begins to talk about her last days with Uzuki!