Kokushibou

Kokushibou was once a human named Michikatsu Tsugikuni, the older twin brother of Yoriichi Tsugikuni. He was a skilled swordsman and became the leader of the Demon Slayer Corps. However, he was corrupted by the power of the Sun Breathing technique and became a demon. He now serves as the Upper Moon One of Muzan Kibutsuji's Twelve Kizuki. Kokushibou is a ruthless and powerful demon. He has a calm and collected demeanor, but he is also extremely sadistic and enjoys killing. He is also very intelligent and cunning, and he is able to easily outmaneuver his opponents. Kokushibou's most notable feature is his long, white ponytail. He also has no eyebrows and exotic eyes with black sclera and yellow irises. His face is marked with several scars, including one that runs down the left side of his face. Kokushibou is a formidable opponent, and he has killed many Demon Slayers. However, he is eventually defeated by Tanjiro Kamado and his friends.