Their Censorship suck then, I've seen Japanese Nude fighting videos, it's not mainstream in Japan but can find it if look hard.
Also, you can google Japanese porn can and find normal fuck videos with no blurred out parts so the law must be enforced on some companies.
There is a company that does matches with really hard face slapping and basic grappling, but the girls start dressed and only see any nude unless there is close ripping during the match.
Competitive fans only make up small numbers of the over all fans in Japan so real competitive matches are hard to find. Your best bet to find the few Competitive shoots that do happen is on Twitter, most of the Catfight producers, fans and models have pages. Need to find the ones that know a little english to help you around the Japanese Catfight world.