Teenage stepsisters Yui and Ai form a close bond as a result of the neglect and abuse from their respective parents. Fearing separation from each other when their parents plan to divorce, they run away together to Tokyo and, in order to survive steal a briefcase which they later discover belongs to the yakuza. This puts them in great danger. Tanida, a kind-hearted yakuza member, comes to their rescue and becomes the protective and loving parent figure they never had. But for how long will he be able to save them from harm?