Eh, as long as the Japanese isn't every other sentence, it probably won't be that annoying. It is kind of cool, in that people who don't speak Japanese won't know what Hideki is saying, so it kind of brings the reader closer to the story - as long as it's not every other sentence, that is. =D You're doing OK so far with it, so don't get too worried about it.

Also, character driven stories FTW. I've actually completely derailed a few plots of mine because once I got a better feel for my characters, I realized that the plot I had planned just wouldn't happen. So keep at it, and know that good characters make the plot more interesting. =D

Interesting characters you've got here! Do you have a planned plot, or are you winging it?

I have to admit that I would probably find the Japanese annoying if I couldn't read it. Plus, you've been skimping on the translations lately.

Overall, I like the feel of this story. Keep it up!