Insanely addictive, and definitely worth playing.
The story centers itself around the Hero (You give the Hero a name), and his two friends, Yuzu, and Atsuro. Where they must contract and fight demons that are mysteriously coming from COMPs (small portable devices that are very similar to the DS Lite in appearance).
The game play is, to put it simply, a strategy game, it's reminiscent of Fire Emblem, but has it's own originality when it comes to fighting. You can also make choices in what to do, and what to say as the Hero. You can control each character and control what they or their demons can do during the turn. Which ranges from healing to boosting stats and of course using elemental magic and physical attacks. The battles tend to either last for a long time or for a short time, which is sometimes frustrating when you want to pass a level as quickly as possible, or was hoping for a better challenge.
There are also other options on your COMP that you can use like, organizing your teams appropriately, buying demons in the auction house (which is updated periodically), and demon fusion, where you can fuse together two demons to make a different demon, for better or for worse. You can also use skill cracking to gain extra skills, which just adds to the strategy of the whole game.
All in all, the game is fantastic and will have you playing it for hours on end with an engaging storyline, and awesome fighting that will keep you on the edge of your seat.