Reincarnated for Billions of Years: I Became the Demon King of Another World

The last survivor of a dead civilization, reborn endlessly across billions of years until name and emotion fade to nothing. Now an immortal monster adrift in the chaotic void between worlds, he wields nanotech that rewrites the laws of magic itself. On a whim born from eternal boredom, he claims the title "Demon King." The world he descends upon runs on pure idealism—thoughts become reality, faith births gods, and ancient races like goblins, elves, and dragons follow mystical laws older than time. But he approaches their sacred magic with cold scientific logic, treating spells as code to crack…