In a remote frontier region, an ageless mage named Dean Nosferatu lived quietly, beloved by the villagers as a guardian deity. His immense power, however, drew the fear of a powerful magic organization that branded him a demon king and destroyed him. Two centuries later, he is reborn as Yuuki, the second son of a baron family. On his tenth birthday, the memories of his past life return, restoring his vast magical knowledge and ability. Rather than seeking revenge, Yuuki resolves to live as a normal human this time, genuinely curious about human society.

Despite his good intentions, Yuuki’s utter lack of common sense and his overwhelming magical prowess constantly pull him into extraordinary situations. He quickly demonstrates his power by mastering ancient magic, saving his older brother, and catching the attention of the kingdom’s princess and a duke’s daughter. His actions lead him to become an apprentice at the Magic Guild, where his abilities earn him renown as a master sorcerer. Behind the scenes, he quietly operates under the alias the “Immortal Mage,” a nod to his former self.

The story unfolds across multiple arcs: Yuuki’s childhood in his noble family, his clashes with corrupted magic users, his participation in a knight selection trial where he pulls a sealed holy sword, and his discovery of ancient magical artifacts and the “Spirit King Cavalry” – powerful relics from a lost civilization. He also reunites with descendants of the village that once adored him, learning that they have kept his legend alive. Along the way, he forms bonds with allies including Princess Iris, the ambitious noble girl Odette, and various magical familiars. The narrative balances lighthearted everyday life, political intrigue within the kingdom and church, and battles against both monsters and remnants of the organization that killed him in his past life. Through it all, Yuuki’s journey is less about revenge and more about learning what it truly means to be human while inadvertently rising as the most formidable mage of his era.