Hagen Kern was a hero who gave everything to the Demon King War, including his Holy Core, so his comrades could become legends.

His reward was a divorce.

His wife, Leysia Edelhart, has become the Sword Saint, while Hagen's depleted rank leaves her looking down on the man she once married. With nothing left to hold him back, Hagen leaves and takes a teaching position at the declining Arcadia High Academy.

His first assignment is Special Remedial Class 7, the class where the academy sends students nobody else knows what to do with.

But eighteen years on the battlefield have taught Hagen something the academy's rigid standards haven't: talent doesn't always look the way people expect.

As his supposedly hopeless students begin revealing extraordinary potential, Hagen finds himself challenging the empire's entire approach to education.

Meanwhile, his ex-wife is beginning to realize exactly what she threw away.