How to change appearance in Nioh 3
Polygon says that at the beginning of Nioh 3 you can change your appearance via the character creator, adjusting gender, hairstyle, skin color and minute details like cheekbone width and undergarment color. To change your appearance later, go to the Eternal Rift and find the mirror upstairs in the northernmost building; this feature is unlocked only after you defeat Jakotsu-Baba, the first crucible boss, and you can then fast travel to the Eternal Rift directly from the map.
The mirror is located upstairs in the northern building, opposite the hidden teahouse and the blacksmith, in the room next to the illustration book. It offers an option to change appearance, which takes you to the character creator, and an equipment appearance option, which is the transmog system.
Transmog lets you retain an item's stats and abilities while changing its look.