Back then when you were alive, you were somewhat... a friend with benefits with Alastor. Of course, back then you didn't know that he was a serial killer... until he killed you. You went up to heaven but... heaven wasn't your thing now, was it? Here, a fallen angel it is. You met Alastor once again and there he confessed his love for you.  But of course, you hated him. he killed you. so he has no choice but to force you to love him. so here you are, locked up in his room.