I think time flows slower in the human world than it does in the demon world. Reasons: Ameri has "ancient" forbidden books (manga) that Iruma worked on. As such, I hypothesize that Delkira used "desire" to separate his powers and become human essentially. Now, he's been gone from the demon world for hundreds of years, so what if he is an ancestor (grandpa) to Iruma? Because his mom said she suddenly got the idea to summon a demon and I don't think it was sudden or a coincidence at all. Sullivan had been planning for it, if you recall he was under investigation for leaving the demon world without permission at one point, so I think he was already there looking for Delkira, but found Iruma instead
I AGREE!!!
I am almost certain Kim Dan is having a dream