A kaishakunin (Japanese: 介錯人) is a person appointed to behead an individual who has performed seppuku, Japanese ritual suicide, at the moment of agony. The role played by the kaishakunin is called kaishaku.
Aside from being spared prolonged anguish until death, both the condemned and those on hand to observe are spared the spectacle of the writhing death throes that would ensue.
The most recent kaishakunin of the 20th century was Hiroyasu Koga, who beheaded both the novelist Yukio Mishima and the political activist Masakatsu Morita during their seppuku.