Mao

Once feared across the realm as the 999th Demon Lord, Mao's fate took an unexpected turn when her arch-rival, the hero Yusha, accidentally botched a spell during their climactic showdown—sending Mao spiraling back through time with all her memories intact, reborn in the body of a young girl. Determined to prevent Yusha from ever walking the hero's path again, she infiltrated an adventurer's school under the guise of a new teacher, scheming to derail her rival's growth from within. Yet her deeply ingrained sense of duty and inability to half-heartedly do anything gradually transformed her into a genuinely beloved educator—one her students now adore more as a charming class mascot than a secret mastermind.