Kokushibo

Kokushibo is a member of the Twelve Demon Moons, holding the position of Upper Moon One.

Appearance
Kokushibo is a tall man with long black hair that he keeps in a ponytail. On his face, he has three sets of eyes with red eye whites and yellow irises. His middle set of eyes features the mark of Upper Moon one. on his face and neck are red markings resembling flames. He wears a patterned kimono with a black hakama. on his waist he carries a sword which interestingly has eyes in the space between the tsuka wrapping of the handle of his sword.

Personality
Mainly, Kokushibo is reserved yet shrouded in mystery. If his actions at the meeting of the Upper Moons is anything to go by, however, he is a punctual, rule abiding individual who places high value in the hierarchy of the Twelve Demon Moons. He is also somewhat humble, as he did not hesitate to admit his failure or complain of any difficulties, instead acknowledging his opponent's strength.

Among his reserved and humble nature lies a more cold side. That is to say, Kokushibo's words can come off as harsh, especially when reprimanding, and his threats can come off as nothing short of cruel and serious, almost overwhelmingly so.

Red Light District Arc
Kokushibo was summoned to a meeting of the Upper Moons, arriving before any of his colleagues. He silently sat facing a wall, only speaking when his presence was acknowledged by the Biwa Demon, and revealing that Kibutsuji Muzan had arrived. Muzan revealed the death of Gyutaro, berating Kokushibo and his fellow Upper Moons for being unable to destroy the Ubuyashiki family and find the Blue Spider Lily. The prominent Upper Moon admitted he had nothing to say in his defense, as Kagaya Ubuyashiki had cleverly hidden himself.

After Akaza brutally destroyed Doma's head, Kokushibo covertly sliced off the former's hand, stating he had gone too far. He explained to Doma that he had not intervened for his benefit, but for the preservation of the hierarchy of the Upper Moon system. He then told Akaza to arrange for a blood battle if he wanted to take Doma's position, asking him if he understood what he was being told. Akaza acknowledged this fact, promising to kill the high-ranking Upper Moon, which Kokushibo wished him luck in before departing.

Dimensional Infinity Fortress Arc
Kokushibo is present in a flashback in Kaigaku's point of view, depicting the time just before he became a demon after Kokushibo defeats the Demon Slayer. He offers his own blood, as that will give Kaigaku more power that he desires if "that man" accepts him as their ally. And as he does, he threatens that if a drop of blood is spilled, the human will be beheaded.

Following Akaza's death, Kokushibo is seen alone. Murmuring how Akaza had abandoned his path to reach further heights and how he had failed to defeat Kokushibo, he reprimands how weak Akaza is. Simultaneously, he reaches for his katana, singlehandedly and instantly slicing the surrounding pillars to pieces in a single stroke.

Trivia

 * Kokushibo bears a striking resemblance to the first Breath of the Sun user. He could be a relative or a co-disciple of the first Breath of the Sun user, or the first Breath of the Sun user himself, turned demon.

Quotes

 * "I... have nothing... to say... Ubuyashiki... cleverly... hid... himself..." Chapter 98, page 15.
 * "You... went too far..." Chapter 99, page 3.
 * "Be thankful for the blood... You are not allowed to spill even a single drop on the ground... for if you do... your torso and head shall have a sorrowful parting." Chapter 145, page 5.
 * "You opened a path... to reach further heights... and you abandoned it... Very weak." Chapter 157, page 5.