The Counterstop Hero's Super Magic Teaching "Over-raise": A Promising Demon King and Princess as Apprentices

Kiri, a summoned hero, has acquired amazing strength as a result of 300 years of training out of caution. He takes Eimu, a naive girl who is the daughter of the "Demon King," as his apprentice to train her to become the most powerful. May, a beautiful sword princess, joins them, bringing her own problems.