Kyoukasho No Koibito summary:

Only energy can replace Oohira Kensuke most important lucky charm-it's a picture of a warrior from the Textbook! Kensuke has been going out with a lover for six months, Sakaki Keiichirou. The most popular man in the company, Keiichirou's real identity is!? Two other stories on Keiichirou's elder brother and his lover as well as a special extra!