Kyouhaku 2 ~Kizu ni Saku Hana Senketsu no Aka~

Saki Akehime is a beautiful girl who has an English mother. She has a secret. She is going out with her teacher, Akito Tsuge, and holding such an immoral secret makes her excited. However there is a figure looking at their acts. One day, Saki receives a phone. Although she is suspicious about the phone, she goes out with Akito not knowing there is a trap full of shame waiting for her...

[From ANN]