Ikariya, Kimura, Takeuchi, Umeda, Nakamura and Omagari (if his presume in mugen train is correct) discarded for Berserker's breakdance based on the way they draw the circle around the numbers in the genga and some of the handwriting.

I think the most probable is Shirai, but there's no genga of him to confirm it. It could also be Takuya Aoki, Ricardo, Yushiro Hatano or Keiko Sasaki, although I doubt is the last one.

Upon further inspection this scene has to be Shirai (+Ikariya AD). The way the clashes flow is very reminiscent of Post #204925 (also similar scene with rotational melee combat being done by the same person wouldn't be surprising). The drawings of the rocks/ground are quite different from Ikariya's too.