A boy in love with his cousin Kasumi also sees her as a sister who wishes to study hard with her help to be in the same school as her. The beginning starts with an open love confession, despite doubting, Kasumi accepts his feelings and quickly embraces him. This strengthens their bond. Aside from this, a friend shows him a porn website and some videos he watches has a girl revealed to be Kasumi. From this point, his life takes a dark turn.