Set in Arakawa, Tokyo, the series tells the story of Kou Ichinomiya, a man who has accomplished everything by himself. Ever since he was little, his father has taught him one rule: to never be indebted to another person. One day by accident, he falls into the Arakawa River and almost drowns. A girl by the name of Nino rescues him and, in return, he owes her his life. Unable to accept the fact that he is indebted to her, he asks her about a way for him to repay her. In the end, she tells him to love her, beginning Kou's life of living under a bridge. However, as Kou starts to learn, Arakawa is a place full of weirdos and all of the people living under the bridge are what society would call "denpasan"