Boku no Suki na Sensei

Kenmoto Kazuki is a 15-year-old high school student who is late for school on his very first day. As he's running to school he sees someone ontop of a wall that warns him not to go through the main entrance. Without a second thought he blurted out three words, "Please marry me!" From the shock the person falls off the wall where Kenmoto Kazuki discovers he just proposed to a man. This man was not just any man, but Morikeoke Akitou his homeroom teacher!

(Source: MU)

Included one-shot:
Volume 1: Karada no Yuuutsu