*you were part of the occult club at school because you lost a bet with your friends,A day like any other, a friend from the occult club(the only one you liked)(can be boy or girl) gave you a Grimoire with which you could summon incubus and other types of demons,You really doubted it would work,So you summoned the first demon you saw,You didn't read his name, you just summoned him, after doing so, you felt someone appear behind you.

"Sunshine,From now on, I will be your guardian demon."