A kid who loves a card game gets pulled into the world those cards came from, and discovers the game was never just a game. The mechanics he memorized become survival tools against a god that's waking up to finish what it started. Real stakes are hiding in the deck-building rules he thought he understood.
Shunta lives for the Battle Spirits card game until a mysterious light pulls him straight into the world the cards come from. Spirits World, the very source of the game itself, is real, and it's dying. A girl named Eto found him there for a reason: an ancient evil is waking up again, the same god-king that nearly destroyed everything before getting sealed away centuries ago. Now that seal is breaking. With Yoku, a confident warrior from another world who controls green-deck spirits, Shunta has to hunt down twelve scattered god-kings. Their combined power is the only thing that stopped the evil god-king once. Whether their old magic will work a second time is anyone's guess. Shunta goes from playing the game to living inside it, and the stakes feel entirely different when real people are fighting for their world's survival. What starts as an impossible quest becomes personal as he learns what's actually at stake.