I'd be happy to volunteer as a proofreader.
As a plus, I can also understand Japanese to a certain extent, so in the process of proofreading I can, at the same time, check the translation and make sure that any proofreading modifications I might make will appropriately match the original Japanese.
With that said, I have to admit I'm not a master of JP, which is why I won't apply as a translator. Sometimes, I'll come across a bit of Japanese, whether a Kanji, a word, or grammatical construction that I don't recognize. But when that happens, I'm usually able to figure it out by looking it up online.