Dude, ayu is a really great lyricist. You don't think she used the term "left side" on purpose? The fact that it could refer to either her ear or heart is EXACTLY why she'd say that instead of "mune" or "kokoro" or something, lol. :)

My personal reading of the lyrics is that when she says "this left side of mine" she means her ear, but when she says "that left side of yours" she means the heart of the person she's talking to.

But yeah, it means both, no point arguing about it. All good poetry has multiple interpretations.

I like this song very much. I find it very powerful and philosophical. Firstly, i thought of it as if something bad's going to happen and she asks, if that person, who was by her side and shared all these good times with her will be still with her and support her anyway.
But now, when I've read your discussion I understand, that partly I was wrong. And the real sens of this song really hurts. She is very strong to discuss it in her songs and share it with her fans.
But, I have a question: we all know, that Japan has different strong-developped technologies, they have so many scientific bases. Why couldn't they preserve her sense of hearing? If she began growing deaf since 2002, why couldn't she make some diagnostics? Operation?