Hey, so I'm actually kind of trying to find a VOCALOID song? Except for it's not really the song I'm looking for, but it's outro.
It was a cover of Paradichlorobenze (I hope I spelled that right), I'm pretty sure, with MEIKO. It cut out a lot of the instrumental parts and started really abruptly. I'm also pretty sure the PV was Project Diva. Anyway, the outro for the video was a human singing the Japanese version of Rolling Girl. It started right at the chorus. The girl singing had a very soft, feminine voice, not nasally at all. Very breathy, I think. It was a custom instrumental, too, very light on the piano. But it was an actual full instrumental, not just a piano cover. Hopefully I've given enough details, I'd appreciate the help. I can't find the original video to save my life.
Edit: More details. I saw the original video no sooner than 2017, and I'm banking on it being closer to 2015 when I actually watched the video. The instrumental was very similar to the original song, not like a hard rock cover or a ballad or anything.