Sekai Saikyou no Maou desuga Daremo Toubatsushinikitekurenainode, Yuusha Ikusei Kikan ni Sennyuusuru koto ni Shimashita

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 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 the story of the most powerful demon king who becomes the strongest hero by mistake.