The choice of the kaishaku (whose job it is to administer the final blow to a samurai
, putting him out of his misery) was clearly one that a wise samurai
would want to consider very carefully. It is a difficult duty, with some odd yet interesting obligations. Firstly, there is no small amount of skill involved. The kaishakunin's cut is supposed to kill the samurai
quickly, but with as shallow of a slice as possible. It was considered poor etiquette
to have the head go flying; doing so was messy (though blood is bound to squirt regardless) and made the process resemble the beheading of a criminal
Etiquette was less important in the battlefield, but some amount of etiquette was always important to a samurai. Ideally, seppuku is a rich (and lengthy) ritual. Conducted in a beautiful garden surrounded by your friends and family, where everyone is dressed just so, and everyone follows the proper forms and obligations. The kaishaku is arguably the most important role in the ceremony (second only, perhaps, to the one actually committing suicide). Learning the proper clothes to wear and the proper actions to take at the appropriate times requires no small amount of study, especially considering there are several schools of thought on the subject. The style in which the kaishaku performs their duties will have a big impact on the ceremony. The kaishakunin must be in a ready to strike on a moments notice, so he must be in a ready stance (either standing in hanmi or crouching in chuu-goshi, or so I'm told), which can be hard on the legs if the principle wishes to recite poetry or somesuch before they die. Yet the kaishaku did not want to make their friend nervous, so they must be careful to hold their blade outside of the samurai's vision. In some traditions the height of the blade is reflected by the status of the person committing seppuku.
Choosing a kaishaku was also at times a political decision. Like choosing a best man at a wedding, you were supposed to choose a close friend, which forces one to evaluate one's relationships. Whoever you choose, others might be offended. Do you choose your best friend, even if he has no manners? Do you choose your wife's brother, despite that you wouldn't trust him to carve the pork of your last meal? Do you choose the blademaster you grew up with, despite that you haven't spoken with him in years?
Properly fulfilling the duties of a kaishaku requires a special mix of nerves and compassion. You are there to end your friend's suffering, so you don't want to delay the final blow unecessarily. On the other hand, your friend is committing seppuku because he has dishonored himself, and wishes to cleanse his honor with pain. If you kill him before he has suffered enough his spirit will bare the stains of dishonor forever.
A samurai committing seppuku has a variety of options, depending on the time allowed and how much pain they think they can suffer. At the very least they should make a nice horizontal cut across their gut, but hardcore samurai might go do far as to try and carve the number ten (juu, which is in all fairness simply an cross, but still a trickly thing to carve when your entrails are spilling across the floor) into their belly. Though the pain and shock involved in either process is immense, it is not necessarily fatal. Meaning the samurai could live on for hours until their kaishaku puts them out of their misery. The kaishakunin is not supposed to act until he is signaled do to so, but even the bravest samurai's mind can become too clouded with pain to communicate when he is ready for his pain to end, thus the kaishakunin must be able to interpret when enough is enough. They must balance their friends pride against their friend's willpower. Strike too soon, and you demonstrate a lack of faith is your friend, yet the longer you wait the more your friend suffers. The important thing is that you strike before your friend dishoners himself by displaying too much of his pain.