Hero's Master Is The Demon King

Demon King Richard was the strongest Demon King in history, but he was also worried about this matter. Because he was too strong, no Hero could defeat him. In fact, no one was willing to be a Hero. He had no choice but to nurture his own Heroes to defeat himself. When he was 777 years old, an accident caused him to be summoned to another world, and the girl who summoned him called him Lord Hero.