The Sakai Clan Armor is the armor of Jin's father, Lord Kazumasa Sakai, which Jin reclaims at Omi Village during Ghosts from the Past. It boosts melee damage and health and extends your Standoff streak, so it is the set for open fights.
Follow the main story in Toyotama to Ghosts from the Past. Jin returns to his family home at Omi Village and takes the armor from the estate.
Pair it with the Charm of Inari's Might for a big boost to health and melee damage. If you wear it into the Sheltered Campsite on Iki before The Legacy of Kazumasa Sakai, the villagers flee and you cannot start that tale, so swap outfits first.
When you start the Iki Island expansion, only the Jin from Yarikawa dye and the basic helmet stay available for this set. Everything else unlocks again after Massacre at Kidafure Village.
Sakai Clan Helmet
Sakai Clan Helmet is a helmet you receive while playing "Ghosts from the Past", from Jin's Journey. It is a story reward, so the tale is the only way to get it.
Sakai Mask
Sakai Mask is a mask you get by finishing "Ghosts from the Past", from Jin's Journey. It is a story reward, so playing the tale is the only way to add it.
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.