Tatsuya Nakadai perhaps became best known for his more devious turns opposite of Toshiro Mifune or his eventual leading turns as Samurai lords in Ran and Kagemusha, but here he plays technically speaking an average man of the 1940's. As the film opens Nakadai depicts Kaji as a pretty normal man who is fearful of being called into military service. Nakadai in the early scenes properly reflects this certain fear that keeps him also from even making a commitment to his fiancee Michiko. Nakadai portrays this in a particularly honest way as there is a certain cowardice in his behavior, even if there is belief behind it somewhere, the way Nakadai at the beginning portrays Kaji simply believes himself simply to not be suited for war. There is a sentiment of pacifism within this, but it is not the overpowering trait. This is evidenced further when Kaji, instead of taking a life sentence in prison for refusing to fight, is able to get military exemption through a promotion in his work. Nakadai does well not to hide the very simple joy of losing his fear of war as he goes about his new assignment, and seems to intent on living again as he marries Michiko since he no longer fears for his life.
The new promotion though is not a easy position by any means though as he is sent to a mining camp in Manchuria, where he will act as a supervisor for the Chinese who are put into forced labor. Nakadai in those earlier scenes set up Kaji well as basically the activist with only a personal cause, and an activist who simply has never faced a personal trial for these beliefs. He's been able to go along with life just fine without having to confront himself, and Nakadai's performance fittingly realizes this mentality in Kaji as he is first welcomed into the camp by the other supervisors. Nakadai brings the enthusiasm of a reformer, but also the naivety of someone who has never reformed anything when he first attempts to start to speak his mind with his new ideas. Nakadai presents Kaji as being appropriately taken aback when he is informed of some of what his duties will actually be such as organizing the removal of excrement, as well as learning that they expect him to bring prostitute to the camps for the workers. Nakadai naturally strips Kaji of this early enthusiasm as he realizes things are not nearly as simple as he imagined they would be in his head, but this is only the first indication that the job is not quite as he might have expected.
The film offers an intriguing perspective as films set in labor camps are more likely to be from the view of the prisoners, but here we are given instead the view of one of the men running it. Nakadai's fairly unassuming approach works wonders in allowing us to follow very closely along with Kaji as he attempts to make his way as a warden of sorts in the camp. Nakadai starts off by showing Kaji struggling a bit just to get his mind wrapped around the procedures, as well as being particularly disgusted by some of the mistreatment he does see. Nakadai brings the needed passion of a man trying to make things somewhat better for these men, and this seems to work. His job becomes more difficult though when he must deal with a new set of workers who are full blown prisoners who must not escape in addition to only working for food. Nakadai is terrific in reflecting the extreme inhumanity in the prisoners arrival where they were starved, and forced into a burning train. Nakadai's exudes well Kaji considerable sympathy for their plight, although it is soon the case that Kaji must still supervise their camp, which is proven to be quite the difficult endeavor from the start.
Once the prisoners show the film adjusts its focus somewhat to include some individual stories in and around Kaji though everything always comes back to him. The strength of Nakadai's work here is the way he portrays a very unique transformation of his character. In the early stages Nakadai presents Kaji as the friendly face who is clearly willing to fight for their proper treatment no matter what. Of course even in this there are tasks he is not proud of and Nakadai is very good in showing the awkwardness in Kaji as he brokers the deal with a group of prostitutes to come to his camp. Worse problems arise when a worker is killed and Nakadai brings the power to Kaji's outrage, but he also brings the eventual frustration though resignation when he finds all the authority figures want to sweep it under the rug or they'll sweep him under it. This leaves an unhappy prisoner population and many of them soon begin to plan to escape. Nakadai realizes in a very genuine fashion how the escape attempts seem to change Kaji as it simply becomes harder to be a pure humanitarian. The difficulty of the job mounts and Nakadai manages to portray how some viciousness can come out of a good man due to a terrible system.
The interesting thing is that the prisoners have good reason to escape yet Nakadai manages to create a strong sympathy in Kaji's difficulty to control them, and gives sense to his actions even when he treats them roughly. Nakadai does not show this transformation as Kaji becoming evil, rather him starting allow himself to be overwhelmed by an evil machine he's a cog of. Nakadai never loses the humanity but shows how it some of it is forced out of him through the horrible requirements of the job. Kaji still tries to fight for them, but Nakadai realizes this with much less optimism, along with palatable emotional turmoil as he only ever comes to barriers in trying to do the right thing. A choice is forced upon him though when the powers that be decide that a groups of the prisoners will be executed. Nakadai is outstanding in the scenes before the executions as he gives the final burst of Kaji's old self as he tries fruitlessly to get a reprieve, and shows how this almost seems to burn him out to a true complacency when no one seems to care. This leads to the executions which he is forced to watch, and Nakadai is heartbreaking as he expresses the despair in Kaji as the men are killed with a sword. Within the despair though that old passion builds and Nakadai gives the needed power to when Kaji finally stands up to the soldiers. Nakadai's particularly poignant as the fear of reprisal is in his eyes, yet he expresses the conviction of to do what is humane is always evident. Now if this were not a trilogy the film likely would end soon after this scene. It continues though to set up the next film with Kaji being tortured before losing his exemption from the war, and being sent off. Nakadai is exceptional in these scenes as well, but what is most remarkable is Nakadai brilliantly realizing this unique arc for Kaji's character from a unearned goodness, to slowly a man complacent with evil, to finally a man who's learned what it means to be and has become a decent man. Although this is just part one of Kaji's story, Nakadai's performance feels complete.