Set in a futuristic Japan where crime has elevated and apathy prevails, Tsukasa is brought up as a boy in order to protect her from the crime-ridden Japan. When the murder of Tsukasa's parents leaves her and her brothers homeless, she finds herself turning to the same people responsible for the deaths of her parents - the yakuza and fellow classmate/Yakuzi head, Ryuji. From their very first meeting, Tsukasa finds herself in debt to Ryuji, and the only way to pay it off is to become his bodyguard. Yet, the incurring debt seems to greatly increase, regardless of how much Tsukasa works. Perhaps Ryuji has other reasons for keeping her by his side?