Conversations with the Khan 7 is one of the Conversations with the Khan records, left by locals during the Mongol invasion. You find it at Fort Imai in Toyotama, and it counts toward the Avid Reader trophy.
Go to Fort Imai in Toyotama and look for the paper or scroll to read. Fort Imai is a Mongol-held territory, so expect to fight or sneak past guards before you can search it.
Also at Fort Imai: the Mongol Artifact Chinese Vase and 4 Sashimono Banners you get for liberating it.
Chinese Vase
Chinese Vase is one of the 50 Mongol Artifacts, pieces of the invaders' culture and warfare you can study. It sits at Fort Imai in Toyotama, and finding 20 artifacts counts toward the Know Your Enemy trophy.
Image: Sucker Punch Productions / PlayStationBamboo Strikes
Bamboo Strikes are button-timing challenges where Jin slices a row of bamboo poles. There are 20 in all, 16 on Tsushima and 4 on Iki, and completing them raises your maximum Resolve.
Charm of Advantage
The Charm of Advantage is a minor Melee charm in Ghost of Tsushima. Ghost weapons deal 20% more damage. You get it by finishing The Cost of Iron or Nattou and the Sake Seller.
Charm of Broken Barriers
The Charm of Broken Barriers is a minor Defense charm in Ghost of Tsushima. Breaking an enemy's guard gives you 15% of a Resolve point back. You get it by finishing Honor Buried Deep or The Delicate Art of Negotiation.