So, to get into the RP, you realize you have to be able to string a bit of Japanese together for your character's name. Unfortunately, you don't speak more than a couple dozen words you've learned from watching anime. And if you plan on doing any world building at a future date (New jutsu? Locations? NPCs?) you'll need to be able to come up with yet more Japanese words.
Internet translations are a lifesaver (assuming you don't rip names directly from other sources). Granted, your made up names will probably still sound retarded to anyone that actually speaks the language, but you'll have a decent shot at getting your point across. The following are the websites that I found useful in my naming attempts:
Google translate
Translates English to Kanji and vice-versa. Not terribly helpful by itself (if you can already read both Kanji and this post, you probably don't need a translator), and not real useful for multiple Kanji put together, but useful nonetheless.
http://www.cs.technion.ac.il/~danken/kanjidic.html
Translates Romaji to Hiragana, Katakana, and Kanji. Also gives possible English definitions for Kanji.
http://www.romaji.org/
Translates Kanji to Hiragana or Romaji.
http://romaji.me/
Translates English into Romaji, Kanji into Romaji, and Kanji into Hiragana/Katakana. I'm not sure how reliable this one is, though, as it gave me some results that were wildly different from the other websites I was using. Seems to work decently for individual words, though.
=)