Mermaid Hour — a school romance adventure game. One of the background characters, "Classmate B," suddenly gains self-awareness and realizes that this world is nothing more than a fictional game. He also notices that no matter what he does, those around him don’t react. With his "slightly pervy" character trait spiraling out of control, he begins having sex with every female character he can get his hands on!
Behind the scenes of the game’s progressing events, Classmate B keeps having sex daily with his favorite main heroine, Shizuku. But despite that, she still ends up with the protagonist, which infuriates him, and he begins to take her roughly. Eventually, Shizuku, too, gains self-awareness—only for the overwhelming pleasure of everything she’s experienced to come crashing down on her...