The plot is quite simple, set in a workplace. The kouhai hears that FMC accepts any request for sex. Then he have sex with her. After that, she seems quite normal, and he secretly meets her again and have sex (if I remember correctly, it was in the fitting room or restroom, or maybe I’m mistaken). Later, the kouhai hear she said that the rumor was spread by some guys who had failed to confess their feelings to her. And she agreed to have sex with him because she liked him. That’s all I remember; I would be very grateful if someone could tell me the name.