Yes, that is Flufferboi's corpse. No, I won't tell you why its corpse found itself in the demon lands. 

...

ACTUALLY when travelling between worlds it's not all up to chance where you end up in, usually it's a world that is somehow linked to you. Memories, origins, desires, it's a mix of everything that directs you to where you'll go to next. Especially if you're dying, you might have a final destination to go to. Unless it's a portal that is a door to a specific area of course, much like the Trial gate that the people of Lasceral have access to in case prisoners really go wrong and they need a something more radical and "harsh" for them to possibly be able to function as a being