Not much more, but I've finally found something particular... apparently, Naoto and Zin are dance instructors in a dance studio called Zeal. Naoto is listed in the Jazz Hip Hop section and Jin is listed in the Hip Hop section.
Jin (on the bottom, click the picture for profile)
http://www.zeal-studios.com/instructor/index.html
Naoto
http://www.zeal-studios.com/instructor/hiphopjazz.html
And he's seems to be into kinky stuff... SLAVE DANCE PERFORMANCE:
http://www.slave2002.com/cast.html (and so is Midoringu!)
http://www.slave2002.com/2005report.html
And they have a load of other dancers... check it out, maybe you'll spot someone you've seen already.
I've found it through this site
http://d.hatena.ne.jp/fujihiro/20061113 which also lists some other dancers, including some PVs they appeared in (Amuro Namie, Utada Hikaru, Koda Kumi). I haven't checked all the links yet, so I might find something more.
EDIT:
Here's HIDE:
http://backdancer.blog47.fc2.com/blog-entry-84.html
And SHU-YA:
http://backdancer.blog47.fc2.com/blog-entry-156.html
EDIT2:
OMZG, SHUYA and JIN and others OFFICIAL HOMEPAGE XD check this out!
http://www.geocities.jp/jin11stalkers/
EDIT3:
LOLZ, Hide was in a dance vocal unit CASK, produced by GLE (whoever that is):
http://pksp.jp/cask-1118/
EDIT4:
Apparently, Hide and Shu-Ya also do classes in ALL TEMPO Studio (a lot of info about their previous work here)
http://www.alltempo.co.jp/hide.html
http://www.alltempo.co.jp/shuya.html
EDIT5:
Basically, this blog
http://backdancer.blog47.fc2.com/ tracks various PVs and lives and lists who danced in them, mainly from BoA, Namie and Koda.
And here's a thread in 2channel forum's 'gay saloon'... it would seem they're discussing Shu-Ya's orientation...
http://proxy2.bbsnews.jp/2ch/gaysaloon/1172641610/