My username is actually Japanese as well. The word "kouri" is just a slight misspelling of "kōri" which means "ice"
The kanji looks like this: 氷
I don't really have much of a reason why I chose "ice" over other things though. I've been trying to memorize some basic kanji recently, particularly things that involve the elements, and when I was going through the ones I knew, I felt like this one could make a decent username. :p
My rationale though is that if I could have the power to control any element, I would want it to be ice (or water, if that's the only way)
Actually, Kouri wasn't the name I was originally going to use when I first signed up for the forums. I originally wanted to be "Cobalt." I signed up using the email address I use for a lot of my "fan-stuff", but I never got any of my confirmation emails for some reason, no matter how many times I re-sent them. I tried writing an email to the mods for help, but didn't get any sort of reply. Eventually I gave up and figured it was just something wrong with they way my address was working with this site, so I just gave up on it. I tried again with a second, more public email address of mine and the username "Exile" (you know, things that just sounded cool

) but I was stunned when I didn't recieve any confirmation emails again. It took me a day or two to realize that I
misspelled my email when I entered it in and now that account was pretty much lost forever too... But, I tried one last time with "Kouri" and correct spelling, and it worked right away. In the end, I guess it was all for the better. I've gotten quite attached to my new name
