Alright, First of all. I know Japanese so I can actually understand the game. Secondly I'm going to be pretty brief with the story, so here it goes..
Story:
Basically the godess(?) Cosmos summons all of the main characters from final fantasy I-X and the god(?) Chaos takes all of the main protaginists from final fantasy I-X (respectively) so now they are all battling for 10 of the crystals.
Battle:
First off.. the battle style is AMAZING everyone is unique in their own way.
So basically, the way it works, is pressing O will do an attack that won't do any damage directly to their HP, but it will store up a number in the left hand corner of your screen. now to unleash that number, you have to press square which will do an "HP Attack" this does all of that damage that you have done, directly to their HP. Throughout the game you can level up and get new ability's, and set them in the menu. you can have 3 attacks mapped to each button. [so O, O+thumbstick left and O+thumbstick right are the 3 combos for the set attacks in the game]. Pressing R+X(X is Jump) and a direction will do acrobatic moves and allows you to actively dodge attacks.
There is also an EX mode. basically if you collect enough orbs, you will fill your EX mode gauge. (the gauge being in the Bottom left corner of the screen) pressing R+square, then attacking someone with square, will unleash a limit break, where you usually have to do a combo or press a button repeatedly to perfect your limit break.
Everything in the battle system runs perfectly.
Final Score:
Story: 10/10
Gameplay:10/10
Multiplayer:10/10
Graphics: 10/10
Final Verdict: Must buy when out in US
(note: This review will be changing as I feel like it. if any of you want the ISO to play it *in japanese* just PM me and I can link you to the ISO and a guide to make it easier for you if you don't know japanese)