The new mother-in-law brought by her father after remarriage is an older sister who is not much older than herself. She has a complicated feeling about her family reunion, sharing the kotatsu and touching skin to skin in the kotatsu. The body of a young woman who is too young to be called her mother is lustful and erection. The other two share the same feelings and secretly flirt under the kotatsu. Before long, it develops into sex seriously.
