Rules:
1. Yamamoto starts out in his Bankai
2. Okuyasu has Josuke's intelligence
3. Battle take place in Soul Society
4. Fighters are 50 feet apart
5. No reitsu crush
6. Vanilla Ice may be entered if Okuyasu can't win on his own
VS
The only problem I see for Okuyasu is the intense heat, he is a normal human with Stand powers, Yamamoto's heat was dryin up everything, Okuyasu would have to end the match fast for him to win, otherwise he simply dies from a heat stroke. Other than that he would win since his Stand was able to fight on par with Josuke's FTL Stand, it can also erase space meaning Yamamoto's defense is useless, add in that Okuyasu can freely erase the space around him to teleport or draw Yamamoto closer and then wipe off his head. Or Okuyasu could simply wipe away space and take Yamamoto's zanpakuto and erase it and then that will make it easier for him.
