First print copies include a code for a useful item set which gives players a Sora (R+) card, 20,000 munny, and 4,000 card draw points. If you purchase Kingdom Hearts HD 1.5 Remix from Square Enix directly you also get a battle support set with a Riku (R+) card, 10 potions, and 10 ethers.
Cards like Sora and Riku can be used in battles. Munny is used to synthesize cards and draw points can be exchanged for cards. Potions restore your energy to do actions and ether recovers the necessary power you need to battle a boss.
Kingdom Hearts X[chi] will be a free to play game where you control an original character that travels to other Disney worlds. Virtual items will be sold as downloadable content. An interesting tidbit is Kingdom Hearts X[chi] is developed by Success Corporation, the company behind Operation Darkness, Metal Saga, and Tokyo Beat Down. While Success’ console offerings haven’t always been, well successful, they have been making browser games like Metal Saga: New Frontier and Ring Dream: Women’s Pro Wrestling Great Battle.