A younger brother and his wife (Rio) return to their hometown where their mother, who has dementia, lives with their older brother and his wife for a memorial service. Six months ago, the older brother's wife left, tired of taking care of their mother, and the older brother was left with desires. Meanwhile, the younger brother and his wife are on good terms, but their sex life is bland, so Rio occasionally does it to satisfy himself. Then, the younger brother returns to Tokyo for work. Rio has to stay behind to take care of their mother.