Kou Ichinomiya comes from a wealthy family and his father runs a famous company. Kou is smart enough to already run several high-flying firms. From an early age Kou's father taught him to never owe anybody anything. Because of this, when he does owe someone something he will suffer an asthma attack. He's obsessed with never becoming in debt to another person. One day, Kou falls into the Arakawa River and is saved by homeless girl Nino (Mirei Kiritani). Kou is in debt to Nino for saving his life. With his obsession over never owing something to another person, Kou asks Nino if there is any way he can pay her back. The girl doesn't want anything. Kou persists in paying back his debt to her and finally Nino asks Kou to love her. Kou will then start to live under the Arakawa River bridge with Nino and other homeless persons.