I made a post about this but it didn't get any replies. I went to a music festival in Tokyo that featured a lot of these bands and took some video if anyone is interested. Previous bands mentioned include Lolz in the Sky, Limited Express has Gone, Hijokaidon, Doddodo, and maybe some more.
Have a look!
http://www.youtube.com/user/twingotw.../2/N1X5dAEviyo
http://www.youtube.com/user/twingotw.../1/ehBJuwGUFnI
http://www.youtube.com/user/twingotw.../0/fvfEsRe3JTA
The music in the third is maybe the most interesting... including Hijokaidon... which was totally insane. Let me know if you'd like to identify a band.