In an island casino called the Howard Resort (ハワードリゾート, Hawādo Rizōto), Rio Rollins is a popular casino dealer with the ability to bring good luck to gamblers just by walking past them, earning her the nickname "The Goddess of Victory". Mint Clark, a young child, comes to the Howard Resort with her grandfather and encounters Rio, and the two become the best of friends.

Rio's life soon changes when it is revealed that she is a "Gate Holder", a dealer who holds one of the 13 legendary cards called "Gates", and whoever collects them all will be named "Most Valuable Casino Dealer" (MVCD). To collect all 13 Gates, Rio must take part in special matches called "Gate Battles" with other Gate Holders and gain their Gates to become the most valuable casino dealer in the world.