Once upon a time, in another world, there was a hero named Amane Kaito. He was in middle school when he was transferred away from Earth. While experiencing many encounters and farewells, he protected the world he was teleported to. His achievements were recognized, and he eventually became a noble in a certain country. He was very much active even during his time as a noble, but due to the strong influence that he commanded, he nearly ended up causing a division within the country. Fearing for the worst, he entrusted the rest to his friends before returning to Earth. Three years soon passed by, and he was attending a private high school run by a certain company. Although he got caught up in various accidents even on Earth, he was able to live as a regular student, that is until one day, when a crack appeared in the sky above his school. A deafening roar was followed by a blinding light, and the next thing he knew, he was looking at a familar scenery. 300 years had passed in the other world, but to return back to Earth along with his schoolmates, Kaito would have to once again set out on an adventure.