- 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".