does anyone know the title of this yaoi?

i cant for the life of me remember it. if anyone could tell me from my vague inaccurate description my life is yours. it's a yaoi where the mc is a purple haired character that has to have sex to use powers i think? i think hes half demon and he has a contract with this demon that looks like a little black bat. theres also this blonde priest guy that likes him i think and helps him. my memory is super foggy when it comes to this one