Basically, a samurai commits seppuku or falls in battle far from home. Afterwards, an associate of his (or his commanding officer?) visits his family to deliver the man's sword and his cut-off topknot. The hair is tied carefully and put into a folded paper packet. In the context of the movies, the presentation has an air of doing honor to the fallen, bringing him home and giving his family a bodily memento. (Possibly a Buddhist funeral necessity?) In one case, the associate may also have brought the dead man's ashes in an urn, but in another, that wasn't possible and all he could give them was the topknot.
However, cutting off a living samurai's hair against his will is usually described as a terrible disgrace, symbolic castration and so forth. If he does it voluntarily, he's signaling that he's renouncing the world and becoming a monk. Obviously that's not at all what's intended with the topknot delivery in those movies, but I can't find anything in writing that gives details on the distinction or says exactly how it's to be correctly done, et cetera. I want to use this idea in a story, but I think I need much more background to it in order for it not to seem strange. I'd also like to know what the family would want to do with the topknot afterwards; is it kept in a place of honor, is it buried or cremated?
I have been googling and looking through various books on samurai history for several weeks and coming up dry: keyword combinations of 'samurai topknot, chonmage, customs, cutting, delivery to family, post-mortem' and numerous equivalents. I'm getting lots of references to the Tom Cruise movie 'The Last Samurai', which has a scene with a humiliating forced hair-cutting, and various other sources on outlawing the chonmage hairstyle in the early Meiji. I've also looked up sources on KAL Flight 007, because I seem to recall reading at the time that the almost complete absence of any remains at the crash site was a problem for the families of the Buddhist passengers, who couldn't hold a funeral without some bodily item present, even clothing. (This may have been a misconception on the reporter's part, since I can't find anything to back up that impression. Or I'm just wrong -- it was a long time ago!)
Any suggestions are welcome!