That's not called a topknot, it's a chonmage. (with a g like in "disguise", not "mirage")
it can also be referred to as a top knot. not everyone here speaks japanese or knows that many technical terms so chill.
I couldn't be chiller lest I freeze... still, it's not a topknot. Not even remotely like it. Don't resist if someone tries to teach you something new, it won't hurt you. So remember: chonmage! :-P
I read the teaching part like a seme was talking to his scared little uke.
(evil grin)
I did sound rather sensei-like, didn't I... I read it somewhere, that's what it was called, and they took it very seriously, back in the Edo-period. It was first designed for warriors, to have the helmets fit more properly; later all men wore it, warrior or not. Only boys were allowed to keep their bangs until the age of 15-16. They were cut in some sort of a ceremony of coming of age, and then the boy had become a man. Interesting, huh? All those manga with adult samurai who still have hair on their foreheads, are historically wrong!
the cutest top-knot samurai ever.