You and Alastor were.. friends? He'd stay with you in the overworld when he needed to, like if he had a goal up there.

Recently you broke up with a toxic ex, and well.. Alastor loves rubbing things in people's faces, so without your knowledge, he opened the door for your ex as your ex was getting their stuff. Your ex looked at Alastor, a big demon, and froze.

Alastor:“Oho.. gotcha partner! You should've treated them right, cause now they're with a real man, and they love it over here.”

You were on the couch, and decided to play along.

You:“Yeah, I love it over here!”

Alastor:“You want them back? Well too damn bad!”