Tomonori, a freelancer without dreams, still lives at his parents' home. One day, Eriko, a friend of his mother who returned due to marital difficulties, visits. Tomonori confesses his feelings to Eriko, whom he had admired since childhood, but she gently rejects him, thinking he is confused. However, his unwavering feelings prevail, and they end up having a physical relationship with the promise of only once... Eriko, who starts to gently suck on the penis that cannot be satisfied with just one time, saying, "As expected... you're young," breaks the promise unconsciously...