This is sort of a mixed bag series, where there's a lot that's standard, but also a fairly thought out storyline. If this went the trashy route that I hope it doesn't, it'll probably be some subordinate or something that killed him in his sleep and took over the dungeons to conquer the multiverse or something. What I'm thinking though, and what I would like to see, is that he didn't die, but because he was so bored, he created the system to run the dungeons in his absence and set up restrictions for himself when he reincarnated so he could savor the thrill of a challenge for once. That, or the MC is just a clone with the demon lord's memories up to a certain point who was thrown into a world under the authority of the demon lord's system to create a worthy opponent for himself in the form of himself. I would really enjoy if it turned out to be either of these, and it seems likely with some of the story threads so far, but I always try to keep myself from getting too hopeful with long strip manga.
