Kaishaku (to assist someone committing hara-kiri by beheading him) (介錯)

Kaishaku (to assist someone in committing hara-kiri by beheading him) refers to cutting off the head of a person committing Seppuku (Japanese ritual suicide by disembowelment) with a katana (sword) for the purpose of relieving the person's agony of disemboweling. Since the mid Edo period, Seppuku was simplified and ritualized, eventually reduced to a so-called Sensu-bara pattern, in which an assistant swung the sword down onto the person committing Seppuku the very moment he reached for Sensu (a fan) which represented a short sword or Wakizashi used for disemboweling. Several techniques were developed for beheading a person with a sword, such as striking the sword into the neck joint, and leaving a skin remaining between the body and the head, depending on the rank and province of the person committing Seppuku. Many cases are known where an unskilled swordsman missed his aim and blundered in beheading a person or broke the sword. For the purpose of averting such a shocking disgrace, the assistant was chosen from master swordsmen. Masakatsu MORITA, who acted as assistant for Yukio MISHIMA's Seppuku suicide, not only failed in his two attempts to behead Mishima, he also bent the sword.

The word Kaishaku broadly means assisting (or taking care of) without limitation the occasion of Seppuku. In a theatrical performance, Kaishaku refers to assisting (taking care of) someone.
In classical entertainment, such as with the Bunraku puppet theater, for example, Kaishaku refers to handing over stage properties
In the modern theatrical performance, Kaishaku refers to such tasks of opening and closing the curtain and supporting performer's action. Even a tool named Kaishaku-bo (a lever used to change the angle of light on stage or the like) is used.