After Nino rescues him from the Arakawa River, a young businessman who cannot bear owing anyone a debt agrees to become her boyfriend and live beneath a bridge.
Kou Ichinomiya has learned to treat self-sufficiency as a family rule. The riverside community gives him people whose habits and claims do not fit his usual measures of success. His attempt to settle an obligation becomes an ongoing relationship with Nino and the other residents.
Nino’s rescue creates the debt Kou insists on repaying, but her request does not work like a business transaction. Living beside the river brings him into a community whose relationships cannot be settled through a single payment.