Junichi Miyake

A boy who is meant to be 18 years old is trapped in a 13 year old kids body after accepting a demon sword after his home village was burnt down. He must find 8 special crystals while trying to survive with the demon in him.

"Marginal Prince" based off of the hit love simulation game series for girls! Yuta studies abroad in a tiny, far away island in the pacific ocean name Alphonso where he enters the all-dorm, all-male Alphonso Gakuen. However, the school is really a place for the children of the famous . . . and the school specializes in classes on empires and alchemy! And one day, after studying enough at the school, the students become known as "Marginal Princes"! Learn about the stories of fate and trial as each of the students studies to become kings! (Source: Crunchyroll)