This entire idea is based on an entire dream I had about Keith and Markus. Basically Keith is all grown up, moved out, and is living on his own, when he decides he wants to summon a demon for fun. (He was drunk) He got the set from one of his friends, and shrugged it off basically saying “I might as well use it eventually,” long story short, he summons an incubus (A sex demon) who immediately wants to mate with Keith, since that’s his job. Keith fights, struggles, and resists against the demon, and tries to send him back, only to find out he burnt up most of the pages in the book that was used for summoning. Keith obviously panics, knowing without the information in the book there’s no way Markus could get back home. He doesn’t even want Markus in his house, and wants to get him out at all costs, but it’s not that easy… In this universe, Keith is in a normal human world with no magic, no weird hybrid species, just humans. If Markus went out there in his demon form, he would be tested on, hurt, and or killed.