Who is kokushibo

 Kokushibo is a fictional character from the manga and anime series "Demon Slayer: Kimetsu no Yaiba" created by Koyoharu Gotouge. He is a powerful demon and a member of the Twelve Kizuki, a group of the strongest demons serving under the series' main antagonist, Muzan Kibutsuji.

Kokushibo was originally a human named Michikatsu Tsugikuni, who was the younger brother of Yoriichi Tsugikuni, the creator of the Breath of the Sun technique. However, after he was turned into a demon by Muzan, he abandoned his human identity and became one of Muzan's loyal followers.

Kokushibo is known as the Upper Moon One, which signifies his position as the strongest and most powerful member of the Twelve Kizuki. He possesses several unique abilities, including the ability to manipulate his body to create multiple arms and eyes, as well as the ability to use the Moon Breathing technique, which is similar to the Breath of the Sun.

Kokushibo is a formidable opponent, and his battle with the series' main protagonist, Tanjiro Kamado, is one of the most intense and memorable fights in the series. Despite his strength, however, Kokushibo is shown to be conflicted about his past and his relationship with his brother, which adds a layer of depth to his character.