Trivia

Though a frequent on-screen rival, he was good friends with Toshirô Mifune.

Although it was commonplace for actors, evening leading men, in Japan to do their own stunt work in the 1950s through at least the 1970s (when actor's union laws enforced safer conditions on sets), the film sets of Masaki Kobayashi were particularly dangerous for Nakadai. During the filming of "The Human Condition", Nakadai was actually beaten by other actors in a boot-camp scene where his character Kaji is brutalized for rebelling against more experienced soldiers. According to Nakadai, the swelling of his face and some of the blood is real on this scene. Later in The Human Condition, his character collapses in a frozen field and is covered by snow, this was real snow and done by Nakadai himself, who came very near to hypothermia. During the filming of Harakiri (1962) real, sharp samurai swords were used in the battle scenes (according to Nakadai, this is not his only samurai film where real swords were used but is the only one where absolutely no dull, stage swords were utilized), much to Nakadai's very reasonable concern, since a mistimed slash could have been fatal for him or the other actors. Amazingly, no one was seriously injured during filming.

His beard caught fire during the apocalyptic castle-burning scene in Ran (1985).

He played characters of a very different age from his own through his career. In Harakiri (1962), he played a samurai in his 50s while he was 33. In Kwaïdan (1964), he played a 18-year-old woodcutter when he himself was 36. In Ran (1985) he played a nearly 80-year-old war lord when he was 56.

After the embarrassing grilling by Kurosawa on the set of Seven Samurai, the then 19 year old Nakadai decided to work very hard on his acting skills so as to be able to reject any future offer by the director. The part in question was an uncredited extra with a few seconds on screen and Nakadai never found out why he was not simply replaced by another actor.

Was not initially considered by Kurosawa for the part of Unosuke (Mifune's formidable gun-wielding opponent) in Yojimbo. When the chief assistant director Shiro Moritani proposed Nakadai for the role, Kurosawa purportedly replied "I don't like Nakadai, and if a director does not like an actor, he should not cast him as one of the leads." As Nakadai's skills were already widely recognized in Japan at that time, the AD found the Kurosawa's reply strange and inquired which of Nakadai's movies the director had seen. The reply was none, as Kurosawa usually did not watch domestic films. Soon after, having watched all of Nakadai's films, Kurosawa came up with his own proposal: "How about Nakadai for Yojimbo?".

Speaks some lines in Mandarin in La Condition de l'homme 1 - Il n'y a pas de plus grand amour (1959) and some in English in 5 gachettes d'or (1968) but learned these phonetically and is self-described as "terrible" at learning additional languages.

While filming his first appearance on film as an extra on Les 7 Samouraïs (1954), Akira Kurosawa spent more than 5 minutes lecturing on how to walk correctly as a wandering samurai for an appearance that totals about 4 seconds in duration.

He has played both the primary antagonist and protagonist in two different films that are both based on the same novel - "Peaceful Days" by Shûgorô Yamamoto. The former was the character Hanbei in Sanjuro (1962), while the latter was Genta in Kiru (1968).

Although not obvious in the movies they made together, he was taller than Toshiro Mifune. He was also one of the few Japanese actors who could stand eye to eye with the almost six-foot-tall director Akira Kurosawa.

Although perhaps most regularly associated with his works with Masaki Kobayashi, Koyabashi was only his second most prolific collaborator among film directors. His most frequent director collaborators were: Kihachi Okamoto with whom he did 12 films, Koyabashi with whom he did 11 films, Hideo Gosha with whom he did 10 films, 6 films each with Akira Kurosawa and Kon Ichikawa, and Mikio Naruse with whom he did 5 films. The longest collaboration would be with Ichiwawa, with whom he did his first film in 1958, his last with in 2006, 48 years later.

Appeared in a plethora of plays written by Kôbô Abe while working at the "New Theatre" and appeared in some film adaptations (often with screenplays written by Abe himself) of his works. This theatre group controversially introduced avante-garde concepts to Japanese theatre and film, especially through Abe's collaborations with director Hiroshi Teshigahara.

His childhood and teenage film heroes included John Wayne, Gary Cooper and Marlon Brando.

Invited to join the Actors Branch of AMPAS in 2016.