Ten thousand years have passed since the last Galaxian War and once again the Ninverse Galaxy is in danger. A human from Earth is called to save the civilizations in it and wield the powerful Chaos Keyblade. Could he survive in the world named Shadow Realm, where the Yu-Gi-Oh! Monsters live?

Alan, a human from Earth, was transported to a world named Regno Tenebrae, the world of Duel Monsters, where he became a Keyblade Wielder, and tried to save the world. However, in the middle of his adventure, he woke up in the magical world of Cephiro, where he will help the Magic Knights on their quest to save Cephiro and find the reason why he was summoned there.