When Kouzou Akizuki, the stepfather of two teenage girls, announces a family vacation, his daughter Airi is quick to voice her dislike for the plan. Eventually, however, she is persuaded by her sister, Marina, who is eager for the chance to share some romantic moments with their father. Marina, though, will only join them a few days later, leaving Airi and Kouzou on their own. Airi is aware of her father's sexual interests and tries to avoid being alone with him in the same room. Unfortunately, she falls victim to a strong aphrodisiac during the train ride to the hot springs, which Kouzou has disguised as candy. Airi finds herself unable to control her sexual urges—which is precisely what her father has been waiting for.