According to the review on play-asia, it seems decent (but I can't tell you how good the game is myself, as I don't own it or a DS): http://www.play-asia.com/paOS-13-71-9g-49-en-70-ukf.html
As for how much japanese you need to know, I doubt it would be much. I've found most of the import games I've purchased to be rather easy on people who know no Japanese (my friends have tried them), with the exception of rpgs. Obviously knowing Japanese is going to help you out, but you should be fine as this is a fighting game and there isn't that much depth to them.
Yeah, about the Japanese with a fighting game, I wasn't too sure, since, from the little bit that I've read, there seem to be cards which you can activate... But hopefully i'll be able to tell them apart and what they do from the pictures (assuming they have them).
But, since it's Bleach (great story) I thought they might have involved a good story, in which case, I'd be required to know a bit of Japanese to get the gist of it...
Unless it follows the anime/manga storyline, then i'm alright. XD
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