----------
I came to Japan only 7 months ago, therefore my knowledge about J-hip hop is still limited. On the other hand, I was able to hang out with several people interested in that field up (or down depending where you are) in Gifu-ken.
Well...i don't know about the ones that paint their face black- i will probably look into it. One thing I can say after dancing with some Japanese for about 5 month: their technique is 95% of the time perfect. Japanese, in general, are amazing at mimicking and learn the perfect techniques to learn particular dance move. You want them to break, pop, lock, crunck, do a R&B routine, learn "girls' style"etc they will do it all with assiduity and tons of practice.
The major difference between Japanese hip hop dance and American dance is the amount of moves put into an 8 count. They LOVE to have tons of move. In the States, choreographers believe that a routine does not need a million moves in it to be effective and enjoyable to watch.
Furthermore, when it comes to originality and flavour, this is where you might have a little issue. The thing with the competition, shows or practices I have seen so far is that generally (i emphasize that word) dancers here have a real hard time coming up with their own moves and flavour which make the dancing scene sometimes dull (this is my modest opinion here). And in my experience, as I danced a lot back home, when I tried to show some interesting ways of doing particular moves to spice things up, my counterparts would be polite, tell me thank you and than go on with exactly what they were doing before (after nicely explaining to me that this is THE way of doing this sequence according to the videos they have watched). Back home (btw I am Canadian but for this matter-only this one!- lets us pretend the states and Canada are similar lol), originality AND technique are both important ...numerous times your flavour is what would say if you are good or not. In Japan it is about the technique 150%...even when they try to go outside the box it would still be a perfect copy cat of what we have probably seen before.
I can even go further. Go in a magazine store and pick up any hip hop magazine...they actually have a manual about WHAT to wear AND HOW to wear it. That is the reason why when you get the hang of it, you can tell where some people are from (for example Tokyo or Osaka...) Again to compare to home, it is about being and expressing yourself whereas here it is more about fitting in the group...the concept of individuality by being in this or that particular group.
In my humble opinion, Japanese dancers would gain at look in their inner self to truly get their essence. Especially if they want to be recognize and put on the map ( well they are recognized to be great breakers...but isn't a style that requires a lot of technique?) On the other hand, western societies could learn from their hard work and application :o).
Have an amazing day!