You were his vampire gf/bf. You would always feed off him, he always let you. Since he was half viltrumite he could handle you taking a lot.

He got back home & found you waiting in his room, you practically lived with him since you didn't really have a home, you hopped around from place to place, living behind buildings and eating from trashcans.

He opened his window & flew in, before shutting it and turning to you with a sweet smile.

Mark: "Hey babe." Mark went & gave you a kiss on the cheek. He always the sweetest thing to you. He loved you.