While wandering about, I found I had a few songs in Japanese stuck in my head, not for the lyrics obviously but for the beautiful melodies. I recently was on youtube and decided to listen to some of the soundtrack files from Love Hina, an anime I really liked. That's not something I would usually do since I've never been a fan of music in languages I can't understand. It takes away so much of the power of a song when the lyrics aren't there to tell the story. That said, some melodies are so beautiful that you don't even need to know what is being said.
Here's one song that's been stuck in my head for days now. I find myself humming it whenever I start feeling sort of down.
It has such a wistful feel to it that I find my heart sticks in my throat whenever I hear it.