Seppuku is a form of ritual suicide practiced in Japan for hundreds of years.
Many Westerners recognize the ritual, in which a person (often but not always male) slits his own stomach with a sword, thereby disemboweling himself and causing his own death. Seppuku has a long and complex history in Japan, and many associated rituals, among them the use of a second, the kaishakunin, whose primary role is easing the suffering and speeding the death of the person committing seppuku.
The kaishakunin stands behind and to the left of the person committing seppuku (as shown in the staged photo above), sword ready but usually not drawn. Just before the ritual begins, the kaishakunin draws his katana slowly and silently (as a sign of respect).
After the samurai committing seppuku makes the initial cut across his belly and then pulls the dagger back to the start of the cut, the kaishakunin strikes the dying man’s neck from behind, hard enough to sever the neck but delicately enough to leave the head hanging from the neck by a strip of skin.
Severing the head completely would dishonor both the man committing seppuku and also the kaishakunin, so this role was given only to men who possessed great control of their swords.
Traditionally, a kaishakunin was utilized by persons committing seppuku for honorable reasons. People forced to commit suicide as a result of personal disgrace or as a result of criminal acts were not permitted kaishakunin, and forced to die the longer, agonizing death from disembowelment alone. (A death which could take anywhere from minutes to several days.)
All other things being equal…this is yet another case when it’s better to have a wingman.