I think I've got the gist of it. It's about, like, new love, but she's (the singer) all sortof wary of it even tho it's mega awesome.
I missed a line in the transcription. It's one of the "chorus" that is different (aiko always does at least one) This is right before the last "chorus".
Lemme try these two lines:
As I watch, a tiny smile begins to creep across my face
Words are so in adequate; such happiness
Now, before you rip me for not knowing any Nihongo at all, note that my "interpretation" actually fits into the meter of these two lines. I'm showing off my lyrical skizzy, but sacrificing precision. I am not good at exact translation, but I *think* I'm pretty good at interpreting the meaning (in this case, since all the words are familiar to me). I tried doing it the normal way and it just didn't work out. My way is more fun!