I already knew what to expect because I was glutton for spoilers back when scanlations were slowly being churned out and just had to get my hands on everything, but like a lot of part 3, it still managed to surprise, trip me up, and delight me every step way.
During part 3, I was kind of surprised at how little interaction occurred between the Kaiji and Kazuya, save for establishing plot or character points and handing off money, but at part 4 it's just been a barrage of showcasing how their personalities and moral codes bounce off each other. Kaiji sees the graves of the murdered gamblers, cries on their behalf, and rushes in head-on to the gambling battlefield. Kazuya slows him down and invites him out for a meal because hey, doesn't looking at dead people work up an appetite? Kaiji cries over the lives lost, Kazuya just treats it as a part of business or pleasure.
I really love how natural it feels; in the hands of another writer Kazuya's rationalization of the deaths of the gamblers, Kazuya's contrast to Kaiji's "No one deserves that!" reaction would have easily boiled down to "So what? They had it coming!" but here, he actually reasons and acts like he honestly was doing them a favor, and that it wasn't a big deal out of all. I also love what a transition it is from part 3, where Kaiji was spending half the season putting up an act and being forced to think as calculatedly as possible, while here, now that he has no reason to, he's back to thinking with his heart instead of his head and just letting it run wild while Kazuya, meanwhile, takes it all in stride. There's no acting out here, it's all completely honest.
It's also interesting because, unlike Funai, Ichijou, Tonegawa, or just about any other of Kaiji's opponents (save for, surprise surprise, Kazuya's own father, the chairman) Kazuya doesn't belittle Kaiji for his beliefs or reactions, but reasons out his point of view and, if Kaiji doesn't buy into it, he just handwaves it like it's not a problem. At worst he just expresses amusement at it, yet even that doesn't come off as looking down at him.
I love their dynamic a lot, it's hilarious and fascinating to watch, and I'm psyched for what's yet to come.