Actually killing NPCs in the previous Fromsoftware games was the only way to obtain certain unique items/spells, Sekiro is the only game where killing NPCs gets you literally nothing of value.

After killing Owl but before going to the Fountainhead palace, I cured Dragonrot for the first time this playthrough. I then gave the red and white "flower" to Kotaro and sent them to the peddler. The peddler was still alive at that point, but I can't seem to trigger them moving to a the last location.

To anyone reading this with the same problem, I figured it out. It will happen AFTER Divine Dragon fight, and as someone else said, stock up on candies before that happens. Cheers.

actualy its about translation man, some game with japanese language were wrongly translated [diferent accent, phrase, and diction] so you feel diferent atmosphere and it makes you sad / not sad / funny / curious,, for the example: Monster Hunter World,, the atmosphere there shoulde be curious research & funny hunting,, but if you set it in english audio or english sub & dont know japanese language/culture/accent im sure it will feels plain and boring,,

it will appear in your donation box I believe.