Gifted with a crest of creation, Gaius becomes the world's strongest sage but seeks a combat-oriented crest. Reincarnating as Mathias in a future where magic is fading, he obtains his desired crest, now seen as the weakest. Excelling at the royal academy despite magic's decline, Mathias uncovers the cause—demons—and strives to undo the repercussions of his absence.