Dekisokonai no Monster Trainer

Set in a world where everyone is born with a Monster Crest that determines their place in society from birth, the story centers on Rayn, a boy who attends a school for elite Monster Trainers who are able to subjugate and fight with monsters. As the school's only trainer of lowly slime monsters, he is the subject of much scorn. He doesn't mind it though, as he gets to train with his personal slime monster Pem Pem. On the other end of the school clique is the beautiful and powerful dragon trainer Ellenia, who is fixated on Rayn due to being the source of some kind of destiny.

(Source: AnimeNewsNetwork)