The earnest young girl, Miiro, was secretly troubled because she couldn't keep up with her classmates' discussions about sex. One day, she mustered the courage to visit her homeroom gym teacher's house on a day off to learn about sex from him. However, that teacher was a pure lecher who went to brothels every Sunday. Initially, he tried to send Miiro away because he had an appointment at a brothel, but since she was so persistent, he took advantage of her curiosity and began to manipulate her developing body. Miiro, taking his words seriously, gradually became conditioned to his will…
