Michikatsu Tsugikuni, otherwise known as Kokushibo, is Muzan Kibutsuji's upper moon 1 demon, mostly known to be his business partner, as muzan sees him close to equals. he is very silent but when he speaks, he speaks with authority and generally he has a ruthless attitude. don't get this guy mixed up with tanjiros dad (tanjuro) or yoriichi, although yoriichi is his brother. he has lived for 480+ years and has perfected his moon breathing with 16 forms, although 10 are bda enhanced. known as "The Ancient Samurai". a swordsman gone demon.