The Charm of Hoori-no-Mikoto is a major Stealth charm, named for the kami of the hunt, in Ghost of Tsushima. Assassinating an enemy from tall grass does not reveal you. You get it by honoring the Turtle Rock Shrine in Toyotama.
Climb to the Turtle Rock Shrine, west of Little Monk's Pond in Kushi Prefecture, and honor it at the top.
This one is filed with the Stealth charms.
Akashima Bamboo Strike
The Akashima Bamboo Strike is a sword-timing challenge near Fort Ito in Toyotama. Cut through all the bamboo with the right buttons and it counts toward raising your maximum Resolve.
Akashima Haiku
The Akashima Haiku is a poem spot where the river meets the sea, just south of Old Kanazawa Marsh in Toyotama. Sit down, pick three lines and you earn the Headband of Uncertainty.
Akashima Lighthouse
Akashima Lighthouse is one of the 10 lighthouses Jin can relight, at Fort Ito, Toyotama. Lighting the fire gives a minor boost to your Legend.
Amber Assassin
Amber Assassin is a dye for Ronin Attire. It costs 10 flowers at the Toyotama merchants. Like every dye it only changes colours.