Why Did Sato Cut Off His Finger If...
If Sato had planned on double-crossing all the Oyubans, why did he bother with going through with cutting off his finger?
shareMy theory is, Sato knew the customs and traditions involved in making amends with the Yakuza kingpins. It was also the ONLY way he could get the other bar that is needed to launder American bills.
The last custom is toasting to a fresh start. Sato knew this was his one opportunity to get real close to Ohashi, the primary mover of all things in the world of crime.
The other bosses would be too busy toasting (or surprised that he actually went through with the cutting of the finger) to make a move against him. It was in many ways his one chance to be in an environment completely in his favour and to get away with both bars and his enemies dead.
And while he could have technically have hired someone to kill Ohashi for him, I think it was in Sato's sick nihilist mind (and doesn't respect traditional aspects of honour or respect) that he wanted to kill Ohashi himself (he also knew that the only way he could gain access to the other bar is by making amends and meeting the crimelords in person).
In the Godfather, you'll notice how Michael Corleone secured his power by killing all the other heads of the mob families. Sato was performing a similar sacrament - except he was personally killing his top opponent.
But ultimately it was just his way of securing his power and gaining all of their turf, while stealing the other bar and being able to launder all the money he wanted to.
He was showing them that he was a true Yakuza.
"Two tigers cannot live on the same mountain"
I used to wonder the same thing, but I agree w/ sic
I'd forgotten that he didn't have the second plate yet, and needed to cut off his finger to get it (for all he knew, it was hidden out of the country)
I'd only add that, now that he's missing a finger, he's got more "cred" with the surviving yakuza. He's demonstrated that he's hardcore and has the stump to prove it.