Sword fights? Not a one is mentioned, though there is casual reference to protecting territory. Even this, however, is inferred as being low-level - no killings if it can at all be avoided. This seems mostly to the complex web of interrelation between one Yakuza gang and the next - somebody in one gang owes somebody in every other gang a favor or two.
Tattoos? Not a one famous Yakuza tattoo is mentioned in the entire book to my recollection.
Missing digits? One incident of this being mentioned (with no other references to Yakuza missing digits in their descriptions) is mentioned and it lacked any and all ceremony that we have assumed was the way it was thanks to the entertainment industry.
Fear at every turn? Sure. If it's not a rival gang encroaching on your territory, it's the police who hate Yakuza with a passion. Jail is pretty standard for Yakuza and the prisons at the time made Hell look like Club Med.
Contrary to the Yakuza of today (or perhaps the Yakuza of fiction) during WWII the main source of income for the Yakuza was gambling, though they dabbled in black market (though not illegal) items whenever they could. Sure, every now and again they sold guns, but more often than not, their version of the black market sold items that were simply in short supply or limited by the local laws. In addition, more than protection money they were into legitimate protection - if their neighborhood is an unsafe place, who comes there to do business or gamble? It was in their best interests to keep things in their neighborhood safe and keep the merchants happy and rich.
The biggest thing to look forward to as a Yakuza oyabun appears to be the same things that you associate with any businessman. They have to maintain a steady income or set some aside for a rainy day, pay overhead, make sure the right people are happy with you (read as: bribe) and want to conduct business with you, keep an eye out for good talent to add to your ranks, etc. Definitely not the posh lifestyle that one associates with the leader of a mafia-style family.
I've rated this book as a 3, but not due to lack of content. Rather, in contrast to the Yakuza as I've grown to know them through the movies and other media this version just seemed watered down and boring in comparison. Sometimes fiction is just more interesting...