Lucifer, the strongest Demon king has ruled the demon race with his overwhelming power.

Making a Harem with his dearest wife, he spent several hundred years eating, making love and sleeping.

Tired of sleeping, the Demon King began to seek for a powerful enemy.

Why doesn't the hero come to subdue him? Even though he's been waiting for so long.

Lucifer then turned himself into a human, and decided to go and see the military academy, which is a training institution for the heroes.

The best way to know what's inside is to enroll in the school.

He quickly passed the entrance exam and enrolled safely…!?

This is a story of the most powerful demon king that becomes the strongest hero by mistake.