Have you heard of this group, 黒人天才 (Black Prodigy)? Black american rappers, based in Japan.
http://404er.com/blog/image/kokujin-tensai.jpg

DANSU DANSU DANSU

Uh.. I guess that's flowing.

And this isn't in Japanese, but it's hilarious nontheless:

I love stumbling on crazy stuff like this through google japan's image search.

殺す

Considering how every verb ends in an -u and every adjective in an -i or na, you'd think that they could flow better.

I really like the way 氷　has 水　written on his shirt, If it was intentional all god but if not...

All said and done, they're probably popular amongst the hiphop Japanese crowd.