The new mother-in-law that my father brought after remarriage is an older sister who is not much older than me. The skin and skin that come into contact with each other in the kotatsu with the family's unity and kotatsu in a complicated mood. Erection with lust for the body of a woman who is too young to call her mother. Two people who have the same feelings and secretly flirting in the kotatsu. Eventually it seriously develops into sex.