Tetsuya Nomura confirmed work on a new Kingdom Hearts side quest game coming to Nintendo DS, and other handheld/mobile platforms. The game will try to explain what Mickey Mouse did in the World of Darkness, how he got his keyblade, and will focus on developing the Roxas character. Nomura hopes that the game will differ slightly from previous KH games and that the gameplay system might be a little different.

Looks like that “hearty system” was the DS.

Kingdom Hearts Network