【 Corruption of a serious man 】

Ordinary student Hara Taiga is drawn to a mysterious Hanai Chisa sitting by the window. One day he builds up the courage to confess and she accepts. Happiness is overshadowed by confusion when she takes him to the men’s bathroom. Contrary to her innocent appearance Chisa turned out to be a perverted masochist…?!

It's an anthology series, every chapter has a set of new characters and situations.