"Rabu Monsuta" ("Love Monster") by Riko Miyagi 12 volumes
Hiyo was lured into entering SM Academy by a boy who calls himself as her fiance. She then discovers that SM Academy stands for Saint Monster and yup it's a school for monsters. She will also uncover the big reason why a human girl like herself was enrolled to this school and engaged to the monster president.
The story and art has a childish appeal and is fairly decent but I was grossed out with the ecchi scenes! It isn't a romantic or sweet ecchi. It's more like a disturbing and perverted ecchi. I even wonder if the name of the school is a pun. I was optimistic when I read this because it's on the top ten of an online manga site. It might have been popular for the wrong reasons. Definitely not for underage readers.