It is not DJ Satomi's daughter or sister, it is Valentina Dante aka V. Dante, a friend Satomi met at university and later became a member of Satomi's projects Supasonic and DJ Satomi.
First, we know that Valentina Dante sang DJ Satomi - Waves, discogs below
Now listen to it, DJ Satomi - Waves ( Slow )
Compare the vocal to Dj Satomi- Castle in the sky (supasonic mix)
As the vocal is pretty much the same, they are sang by the same vocalist, Valentina Dante in this case.
More info about DJ Satomi. DJ Satomi is a project by three people, Simone Bocchino, Giuseppe Borgoni and Valentina Dante, their former project was Supasonic.
Other Satomi and Giuseppe Borgoni's projects
Dogma (2), http://www.discogs.com/artist/187026-Dogma-2
Only one hardstyle track, Dogma - God Machinery
Dr. Jacobs, http://www.discogs.com/artist/214964-Dr-Jacobs
Only one track, Dr. Jacobs – Lobotomize
Can't find the track, just a remix in iTunes,https://itunes.apple.com/ca/album/lobotomize-xlnc-remix-single/id268991784
Only one track, M.O.R.K. – Fantasy, not sure how sang the song
Only one track, Megaton – Maphia
Megaton - Maphia (XLNC Mix) [Hard Trance], Megaton -- Maphia (Zatox Remix)
More than one track but I'm too lazy to google them, I guess this is a more successful project before DJ Satomi as this one got a web site
Only one track, XLNC – Ufo Alarm
Can't find the track
I guess this is the little history before Satomi began his project DJ Satomi.
EDIT: Found Satomi's YouTube channel, with one video
Then he made another account as he can't log in the first one any more, explained below.
EDIT2: Found another Satomi's YouTube channel, with two videos this time