Pretty much the entire running time is the war amongst the Yakuza and the downfall of the leaders from the first three movies. It’s solid and compelling but not as twisting as the first three movies as the war plays out to a logical conclusion once the Police get involved.
It also focuses and spells it out more plainly on the benefits of being a leader and how the society preys on the yakuza who do not have power plus also how they dealt with leaders who were in it for themselves.
On a side note it took me until the 3rd movie to realize the series is from the eventual Director of BATTLE ROYALE.
source https://letterboxd.com/jballison/film/battles-without-honor-and-humanity-police-tactics/