In a quiet residential area surrounded by greenery, there was a house where a family of four lived. One day, the mother and eldest son saw off the father and second son as they left for a week-long trip. In contrast to the cheerful mother, Riho, the eldest son was gazing at her supple body as if licking it all over. He had his sights set on the body of the beautiful stepmother who had just been welcomed into the family...