Japanese mud wrestling clips seem unusually hard to find, so I was very happy to stumble upon these:

https://www.youtube.com/watch?v=QVTAh7K4KnE
https://www.youtube.com/watch?v=3xZmbYd_r9c
https://www.youtube.com/watch?v=A8s-PCUg1wI

Should also mention that in the channel those came from there are a lot of "American" mud wrestling clips for those interested (don't know how fresh they are):
https://www.youtube.com/user/7524seimegu/search?query=%22mud+wrestling%22

Also liked these "Girls Going Down Mud Wrestling" clips posted last week by BlingMaster. More like chocolate than mud but damn sexy:
https://www.youtube.com/playlist?list=PLh-HqViDwNng2olXX_XKlTa_YXTUCu0sK