Ooh fun times, Calico, fun times. XD Ya, when I first sang Japanese songs my friends were like "Wow you sing so well!" But then my cover would be blown once I came across hiragana/kanji I didn't know how to read (this was two years ago). Now I just have a bit of trouble with kanji...but other than that, I can sing most any Japanese song if I'm familiar with the tune
Have you ever noticed how a lot of Japanese songs have the same kind of phrases in them? ^^; Makes it easier to sing them once you figure out which phrases are used in them more, haha.