Goofs
Anachronisms
In the road scene, when Mishima and his crew are going to the Ministery of Defence, many models of cars can be seen which existed when the movie was filmed, but did not exist in the year the events happened (1970).
Crew or equipment visible
Shadow of camera and operator on the ground, to the bottom left of frame, as the garrison assembles for Mishima to deliver his address.
Factual errors
Mishima didn't exaggerate his illness. He was declared unfit for military service because of an inexperienced Army physician's misdiagnosis.
The word "country" written in Japanese kanji on the hachimaki is the simplified character. On the actual hachimakis, the kanji for "country" was the long traditional form.
General Mashita wiped the sword with tissue paper, not cloth.
Chiba Koga did not try to strangle Mashita with the polishing cloth. He had given the polishing cloth to Mishima to wipe the sword and used his hands to throttle the General from behind.
It was Morita, not Mishima, who locked the doors. When he saw that some doors couldn't be locked, Mishima ordered them barricaded.
There were two cadets outside the building, not just Morita.
The globe's stand was not knocked during the scuffle.
