Ten years ago, Tsubaki divorced her husband and has since raised her son Shiro all by herself. Through sheer determination, Shiro successfully graduated from vocational school and landed a job. However, due to his long commute, Tsubaki suggested he move out and live on his own—but he refused to leave home. Realizing that Shiro was overly dependent on her, Tsubaki decided to take him on a trip to a hot spring inn, hoping to draw him out into the wider world and encourage his growth as an independent man.