Long Tianci loves collecting all kinds of cards. One day, he receives an anonymous package. Inside is a box of Yu-Gi-Oh! cards, but they are unlike any he has ever seen. They seem almost alive, and the deck contains only Monster Cards, with no Spell or Trap Cards. Curious, he studies them for a long time but cannot figure them out, so he eventually gives up. Then one night, with the blood moon overhead and lightning and thunder raging, Long Tianci hears a summons in his hazy sleep. It is a woman's voice, clear and sweet: “We need you. This world needs you. The Demon King has awakened. Come quickly…”
He suddenly opens his eyes and finds himself in an unfamiliar room, with that strange box of Yu-Gi-Oh! cards beside him. Little does he know that an extraordinary journey to another world is about to begin. From that moment on, Long Tianci sets out on an adventure to save that world and defeat the Demon God.
