Her sister is a masochist

Me and she are college students. Her younger sister Nanami is a high school girl. Nanami had a quiet face and was actually a masochistic woman... One day, Nanami realizes that I'm watching and shows her masturbation and seduces her. I was surprised, but I decided to train my perverted little sister. Masochist training is repeated despite her eyes... Her relationship with her sister escalates day by day, and she ends up becoming a completely masochist female who repeatedly climaxes through bondage sex. #YoroP