The main character of Hentai Shiina Chizuru is studying at the Wakasa Senior Academy in her second year. She is incredibly strict and pedantic, for which she is not very popular among her peers. The girl is secretly in love with the tall and beautiful Tsukino-sensei, who meets all her requirements of the "ideal man". However, there is an old pervert teacher at the academy, Tamura-san, who chose Shiina Chizuru-chan as his sex target. Tamura-sensei has developed a whole plan that will give him the necessary advantage. He throws money from the academic "general fund" into Tsukino-sensei's personal belongings, making him a thief-scoundrel and a little later reveals this "terrible secret" to Chizuru-chan. The girl is ready to do anything to protect and save the honor of her lover. Tamura-sensei, with the help of a small trick and blackmail, completely enslaves the mind and body of a rebellious chaste anime beauty.