Creativity and Seppuku

Seppuku: Japanese ritual suicide. Samurai were honor-bound to commit seppuku if captured. It was an honorable death. In 1970, Yukio Mishima, one of the most important Japanese authors of the 20th century, shocked the world by committing seppuku. On November 25th, he sliced open his stomach inside a government building. Why did Mishima kill himself?