During a family trip, the mother, concerned about her son's virginity troubles, challenges herself to a reverse prostitution job where she offers to impregnate him for 100,000 yen with a single shot. Initially bewildered, the mother, driven by her love for her son, makes up her mind for the reverse prostitution. Awakened, the son, knowing it's wrong, still inserts his virgin penis into his mother's vagina. Despite the father sleeping soundly just 30 cm away, the two are unsatisfied with just one ejaculation and repeatedly have unprotected sex.