My father remarried and brought me a new mother-in-law who is not much older than me. - 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.