Although the appearance of the gun of course establishes Unosuke as a threat, as everyone else is fighting with only swords, he is truly established as such by Nakadai's performance. Tatsuya Nakadai a very interesting actor as he has such almost breezy manner in his performances yet his presence is always clearly felt. Nakadai's way about the screen is pretty much a perfect match for Mifune, and it is easy to see why Kurosawa cast Nakadai as the villain against Mifune once again in the sequel to Yojimbo, Sanjuro. With all the other villains it is obvious that Mifune/the samurai seems to command over all, but once Nakadai shows up the samurai plan seems like it may not be so easy anymore. Nakadai as Unosuke makes a worthy adversary for Mifune as the samurai.
Apparently Kurosawa told Mifune to play the samurai as a wolf which helped him create that distinctive twitch, and he also gave Nakadai an animal in mind but for him it was a snake. Mifune made brilliant use of the idea and so does Nakadai. Nakadai also is a very physical performer and the way he infuses the "snake" in to his performance is remarkable. Where Mifune had the broader movement of a wolf, Nakadai is very withdrawn as he slinks around so smoothly making Unosuke stand out very well among the group of slovenly criminals around him. One of my favorite movements Nakadai employs is the way he pulls out the pistol he moves his arm very much like a Snake preparing to strike. It is later said that Unosuke feels the pistol is an extension on himself and Nakadai realizes this quality quite beautifully.
Unosuke technically speaking is not even the main villain since he actually is not even the head of his own gang. Nakadai thoroughly commands in his scenes with his substantial charisma and he most importantly challenges Mifune in every scene they share together that further emphasizes that Unosuke is perhaps a match for the samurai. One of the best scenes in the film is when Unosuke confronts the samurai over the disappearance of a woman who was being held captive by his gang. Nakadai's reaction are terrific in the scenes as he has that piercing and so very sly of a stare as Nakadai suggests that Unosuke is constantly taking apart the samurai lies. Mifune and Nakadai play off each other exceptionally well with Mifune and Nakadai trading the right knowing glances as Unosuke and the samurai try to outsmart one another.
Nakadai like Mifune is quite entertaining by really having so much fun with the role. Nakadai is rather cleverly entertaining in his depiction of Unosuke who he gives this terrific smugness. One of the most memorable qualities of this performance is that absolutely perfect smile that comes to his face whenever something happens to be going his way, or if he ever is challenged by someone. Nakadai's smile honestly almost looks like a cartoon snake, and it is just so good in portraying the extreme deviousness of Unosuke. The pistol of course gives Unosuke a terrific advantage over all the other fighters. Nakadai's sleazy pompousness is so great because Nakadai shows that Unosuke knows of this advantage, and just loves the fact that no one seems to have a chance against him.
Tatsuya Nakadai gives a great supporting performance and serves the film wonderfully by making a villain worthy for Mifune's nameless samurai. Nakadai's performance feels effortless in creating the substantial menace he carries with his performance. Like Mifune he as well makes the most out of the animal basis for the physical elements of his performance. Like Mifune once again all of the animal manner seems completely natural to his character, and only makes Unosuke stand out all the more as a character in the film. When the final duel comes Nakadai creates the needed threat for the scene, and when Unosuke is defeated its all the sweeter just to take that smug look off his face. Nakadai particularly strong in this scene as he portrays that Unosuke is completely lost without his gun and obviously defeated. There is a wonderful moment though where the samurai gives him his gun and Unosuke thinks he has a chance to kill the samurai. Nakadai brings that smile back one more time to show Unosuke confidence is the pistol. Nakadai is extremely effective and makes a memorable demise as he makes the loss of the smile equate to the loss of Unosuke's life. One more time I must say like Mifune's performance in this film, I love this performance.