Released in Japan in 2014 on iOS, PS Vita and then Android, it never saw the light of day in the west.
It's an action RPG that lets you explore a 3D world and take down monsters in small, enclosed, areas.
If you want to see more gameplay, here you go:
Surprisingly, Square Enix is still trying to re-release the game in a different form. An offline app might be on the cards then. We'll have to wait and see if that will be limited to Japan too.