Anyway. To be back in topic, here is a "demo" version of Heartless. The lyrics are actually great and the voice... Awesome.
-EDIT
The singer is the composer of the song, she's in the credits. The song is quite old, from 2009. Shanna is also in the credits of Can We Go Back, also from 2009, so this could be one of the cases of a song that Kumi had in her catalog way before releasing. At the same time is hard to be sure since her voice changed from that time and Heartless sounds like it is with her current "technique".