Years ago, packs of people were suddenly drawn in to an unfamiliar world. Their memories discarded and a mysterious power placed in their hand, everything was thrown off. After years of conflict and power shuffling, society melded itself back together and a new era begun. Nowadays, cards are used for entertainment as sporty arena matches where card users test themselves to build a name. All of this is unknown to Aiko, who suddenly appears in the men's restroom.