The main character, Masato's tutor was evil childhood friends! His mother asked for them to tutor him because of his poor grades. These sisters have been abusing him for a very long time.

During the tutoring sessions, the Shinjo sisters use him as an outlet for their stress, which weakens him both mentally and physically. Then one day, he meets Ootomo, the owner of a secret club called “Gentil Donna”.

The hypnosis device he borrows from Ootomo will soon involve not only the heroines, but also all the other people involved in the club.

[From Official website]