The Hashira and Tanjiro dress up as people related to them and spend a week that way (because demons are unable to attack for one week).

Tanjiro → Yoriichi Giyu → Tsutako Rengoku → Senjuro Sanemi → Genya Muichiro → Yuichiro Obanai → Koajima Shin (Name of the Serpent Hashira in the Sengoku period) Mitsuri → Nezuko Shinobu → Kanae Tengen → Uzui Kuran (Name of the Sound Hashira in the Sengoku period) Gyomei → Himejima Tetchin (Name of the Stone Hashira in the Sengoku period) Guest → Michikatsu

AI, Michikatsu's clothes are exactly the same as Kokushibo's.