A story that's so good, you wished it was canon.
The story starts out with a force of Hollows attacking the Rukon District. Captain of Squad 5, Seigen Suzunami, along with his lieutenant, Sosuke Aizen, and Captain of Squad 12, Kisuke Urahara, arrive at the scene and quickly dispatch the Hollows. However, one Hollow escaped and tries to eat twin souls, the Kudo twins. Seigen tries to attack the Hollow, but fails to defeat it. He then adopts the two children. Years later, the two become Soul Reapers and join Squad 5. Under the tutelage of Kaien Shiba, the grow into fine Soul Reapers, going on to face down the powerful Arturo Plateado.
There is much more story, and that is more of a brief summery of the first half of the game. Needless to say, the story is fantastic. When you start the game, you can choose to play as the male Kudo or female Kudo and then you can name yourself (the other twin will join using their canon name and canon shikai). After a certain point, you get to decide just what your shikai is. As the game continues, you'll undergo trials so that you may learn another skill (Shunko or Bankai). Keep in mind that I'm also only going off of the Male story, as I have yet to play the Female story (though I heard it's from her point of view, meaning you have to play both to get the full story).
Gameplay is pretty simple. If you've played Devil Survivor or Advanced Wars, just dumb it down a bit and you get Phantom. Each character is placed on a grid and can move a certain amount. When two units collide, they can battle, switching to a battle scene that shows them attacking automatically. Should your Spiritual Pressure be high enough, you can unleash a devastating attack against your opponent. Also, all units are split between 3 catagories: Speed, Power, and Tech. Speed beats Power, Power beats Tech, Tech beats Speed. Simple concept. During your turn, you can move, attack, use Kido (the series version of magic), use an item (which you need to equip pre-battle), Guard, Pass, or (if your Spiritual Pressure is high enough and your character has one) use Bankai. Fighting is easy and fun.
Outside of battle, you can watch cutscenes and are placed on a board. Kon will walk along this board as you watch cutscenes. When he reaches the end, the time is over and you go back to story related missions.
After beating the game, you get to go to something called Mission Tower, where you can play a bunch of different missions using your leveled up characters. I didn't play though much, but you gain skills and abilities that you may have missed through the main game. So, they just give you everything.
All in all, the game is fun. It can be challenging at times, but it's worth it to finish the amazing story. I highly recommend this game for a fan of the series or tactical RPG fans.