[Request] Trying to figure out a song with little info... Please help?

[haikudasai]

I heard this song about two months ago on a CM but I don't recall/can't find it anymore.

It's a female singer (hell these days it could even be a vocaloid) and it most notable part is that it has a very soft almost music box tone with her singing a phrase about three times and then the forth phrase ends in an u sound, I believe.

Her voice sounds young with a higher tone. I believe it has a pick up towards the end...

Please help. It's not my normal music choice but I can't get it out of my head and the sooner I find it the better lol.

Thanks

[Polyrhythm]

Could it be.....?