Several years into their marriage, Yumi Kazama and her husband have yet to have children. As her husband's penis gradually weakens, their intimate life begins to dwindle. One day, Yumi joins a neighborhood gathering at the Koda household, where she overhears a conversation about an extremely potent erectile enhancement drug that's difficult to obtain in Japan, sparking her curiosity. Learning this, she obtains a small amount of the drug from Riri, who had already purchased it, and decides to try it that night. However, she accidentally gives the drug to Koda's son, Atsushi, mistaking it for stomach medicine.