A teenage boy gets transported to hell and becomes the demon king after eating the flesh of the demons and he spends a couple of centuries there, I think it was about 500 years.
Soon he gets fed up with eating only demon flesh and wants to go back to earth, which he does.
When he tries to transport himself, he ends up somewhere else before getting to earth. So he thinks he’s in the right place
When he gets back to earth, he realizes that it’s only been 3-5 years since he’s been gone and things have changed.
It’s very similar to like a gaming system society, everyone has ranks and powers and can transport themselves into an MMORPG simulator type world (I hope that makes sense)
He meets a girl after saving her from some bad guys (on earth) and she brings him home because he’s really confused.
Oh and he really wants to eat something, it’s mentioned a good number of times on the first couple of chapters, like he’s really insistent on it and gets mad at some guy for interrupting his supper and beats the crap out of him