Henkyou Gurashi no Maou, Tensei Shite Saikyou no Majutsushi ni Naru follows the journey of the once-feared “Lone Demon King,” who was revered as a guardian deity by the villagers in a remote region. Despite his great power and immortality, the Demon King was destroyed by a powerful magic organization that saw him as a threat. Two hundred years later, he is reincarnated as the second son of an aristocratic family and, once again, possesses the strongest magical abilities. In this new life, he chooses to hide his true nature, vowing to live as a human while avoiding the pursuit of revenge. With his love for humanity intact, he decides to adapt to his new surroundings, despite having little understanding of common human behaviors or limitations.

As a noble’s son, the reincarnated Demon King quickly gains the affection of his family and friends. Although he tries to live quietly, his immense magical talent makes him a figure of admiration within the magic guild. Unknown to most, he secretly becomes the legendary “Immortal Mage,” a title befitting his immense power and eternal life. With his lack of common sense and unstoppable magic, his journey to live a peaceful human life leads to a series of humorous and epic adventures, as he navigates both the mundane and magical worlds while maintaining his mysterious identity.