Momoka works as a school nurse who initiates sexual encounters by summoning the protagonist to her location, compelling their forced participation in sexual acts. She is Maron's older sister, a relationship that becomes consequential when the protagonist encounters Maron privately, triggering further sexual interactions among all three. The narrative advances to a communal setting where Momoka, Maron, and the protagonist engage in group sexual activities at a public bathhouse, culminating in a threesome.