Am I the only one who is not understanding a shit? Please delight me

So heres how im seeing it hope it helps: the hero was killed and reincarnated memories intact, and i think the prince did too but no memories. I think the evil from their world somehow made it to the world theyre in now and has cursed the prince. I feel like it has something to do with why things in their world ended the way it did. Unless demons just exist in this world but it doesnt feel like they should since they mention the gods separated the dimensions for safety reasons. I could be wrong but it just feels like thats what's happening imo

i dont understand too, why the hero killed in the past time line?? did he betray the prince?

I think a demon took over th prince and thats why he killed the hero

ohmy i thought the demon took over the hero...