32-year-old divorcee Koutarou Sakamoto was living a lonely existence until he runs into Hinako Sumioka, a former neighbor who used to come running to him every day as a child to help her with her small problems. 23-year-old Hinako is no longer small, and neither are her problems. She is now a homeless single mother, having nowhere to go with her 3-year-old daughter Minami since their apartment burned down. Koutarou brings them home to live with him, but he soon learns that Hinako is no longer interested in running to him or anyone else for help because she is determined to be self-reliant for the sake of her child. Can he convince her that her "Kou-chan" is still worth leaning on?