Daikenja Riddle no Jikan Gyakko

Riddle was a moderately skilled mage in a moderately important guild when the Box of Malice — a cult he has never been able to confirm the boundaries of — killed every member of his party in a single afternoon. The survivor pact he made with himself afterward took a thousand years to pay off. He has finally, in the present-day frame of the show, mastered enough magic to invert his own personal timeline and arrive back in the past as a teenager. The short-format series is the new run of the same year, with Riddle holding ten centuries of grief and the spell list to spend it on.