pretty sure the vial broken theory is correct, after a calamity (or 2, since its quite likely in round 4&5) both player will be left with no air, and then Baku will pull out his first air-bio which has a little left in it and will watch this motherfucker drown right in front of him.
@299792458 guess we just have to disagree. I don't see how a burned/broken finger would not count (actually you lose when all fingers are pointed out OR if you point out the wrong number so breaking teh finger is insta-loss).
Also no way Baku can cut his opponent's finger, not fast/strong enough...