When 20-year-old college student Haruto Amakawa dies in a traffic accident, he does not expect to wake up in an unfamiliar world in the body of a young boy named Rio. As their memories and personas fuse, Rio realizes that he now also possesses magical powers. He is relieved to find that his burning passion for revenge against his mother's murderers has not subsided, despite his newly changed identity. Not soon after, Rio comes across the kidnapped princess of the Bertram Kingdom and saves her without hesitation. To express his gratitude, the king grants him the opportunity to enroll in the Bertram Royal Academy. Believing this to be a new chapter in his life, he is excited to study at this prestigious academy, but life here proves to be difficult for him, a slum-dweller surrounded by the majestic children of nobles.

After Rio escapes the capital of the Beltrum Kingdom with his former teacher Celia Claire and his bond spirit, Aishia, he finds himself in a dire situation once again. As it turns out, multiple people from his past life in Japan are suddenly scattered around the new world. Rio rushes to their help, saving a small group and taking them under his wing. To his surprise, one of the rescuees is his old self's childhood friend Miharu Ayase. The newcomers were not the only ones summoned. With old friends and new allies by his side, Rio sets out to locate the other abductees while searching for a way to send them back to Japan. However, Rio never loses sight of his main goal: avenging his mother's death.