I just found this game on Japanese App store. Surprisingly, it's free. Kingdom Hearts is the popular one for SquareEnix. The story is about merging Final Fantasy's world with Disney. So no wonder if you see Mickey and Friends with characters from Final Fantasy.
The system is quite same with other games on mobile. You have to connect to the Internet, and choose friend's character to help you pass through each stage. Collecting items in order to upgrade weapons and abilities. each stage has 3 conditions e.g, defeating the targeted enemy in 1 turn, Attacking enemies by 'tornado step'. Using a specific Keyblade.
By the way, there is only Japanese version right now. but the condition is something around here, so no need to worry.
Hope you enjoy playing.