Renai Kyoutei Nukegake Nashi!

Renai Kyoutei Nukegake Nashi! summary:

A childish student, Shirou carries a torch for his teacher, Oka. Masami, a good friend of Shirou's, who has cherished him like a brother, is confronted by Ryuuji, another friend of them, concerning his true feelings for Shirou. Masami and Ryuuji conclude a gentlemen's agreement, in which either of them cannot hit on Shirou. Ryuuji orders Masami to substitute and take care of his sexual desire instead of Shirou.