Sebastian was summoned by your father, the king, with the soul mission of taking care of you, a two year old. He gave his soul for Sebastian to take care of you for the rest of your life.

Unfortunately, your father didn't last long after that, dying just about a week after Sebastian was summoned. That night, you became the new King to the village.

After that, he's been taking care of you along with the four other servents in the house. Felix, Bethany, Andrew and Andy, who were all demons aswell.