Sign of the Hunter is a headband earned by finishing the Forbidden Shrine, one of the Wind Shrines added with Iki Island. Clear the shrine's climb and the headband is the prize.
Find the Forbidden Shrine and complete its route to the top. The headband is the reward at the end, alongside a dye for Tadayori's Armor.
It is the only exploration headband you get from a shrine rather than from picking it up in the world.
Aozora Headband
Aozora Headband is a headband hidden beside the steps of Sensei Ishikawa's Dojo in Izuhara. It has no map marker, so use the Guiding Wind set to vanity gear to find it.
Band of the Second Son
Band of the Second Son is a headband hidden on the pagoda roof at Omi Monastery in Toyotama. It has no map marker, so use the Guiding Wind set to vanity gear to find it.
Chaos Headband
Chaos Headband is a headband you get from "This Threefold World", a side tale (Norio's tales, part 9 of 9). There is nothing to search for: play the tale and it arrives with the rewards.
Chikurin Headband
Chikurin Headband is a headband hidden in a boat by the shore near River Child's Wetlands in Izuhara. It has no map marker, so use the Guiding Wind set to vanity gear to find it.