Rui

Lower Moon Five. His hobby is string figures. He is the youngest member of a family of demons living on Natagumo Mountain, a small boy with a spider-like hairstyle. He has been a demon for just under twenty years. His strength is considered high among the Lower Moons, comparable to that of Lower Moon One (Enmu) and Lower Moon Two (Rokuro), and he was favored by Muzan. He is usually calm, but when he gets angry, he becomes emotional and his attacks become monotonous.

He has demons playing the roles of "mother," "father," "older brother," and "older sister" under him, claiming bonds with them as the "youngest brother," but in reality, he controls them through fear and violence. His statements and actions are obsessive. There were more family members before, but they were reduced to four because those who defied him or failed to act as a family were executed. The demons playing family roles originally had different appearances, but their faces were forcibly altered by Rui. Rui hated it when his family reverted to their original appearances and frequently abused the Mother Spider, who often reverted to her child form.

He possesses Blood Demon Arts that enhance his threads with his blood, giving them hardness surpassing steel. He can form them into a web without losing their sharpness.

His name as a human was also Rui. As a human, he was very sickly, unable to get out of bed, and even walking was painful. One day, Muzan gave him blood, turning him into a demon. After becoming a demon, he had to continue eating humans. When his parents learned this, they attempted a double suicide, but driven by a moment of rage, he killed them.

He fought against Tanjiro and Nezuko on Natagumo Mountain. He was moved by Nezuko's bond with her brother and decided to make her his new "sister." He showcased an overwhelming difference in strength by breaking Tanjiro's Nichirin Sword with his threads. However, the Kamado siblings, having awakened new powers, counterattacked, but Rui cut his own head off before Tanjiro's sword could. Enraged, he attempted to kill the Kamado siblings but was finished off by the arriving Giyu Tomioka.

As his body crumbled, he realized he had severed his parents' life-threatening love with his own hands. After death, his soul reunited with his parents, and he apologized, disappearing into the flames of hell together with them. In this battle, Tanjiro failed to collect the blood sample from the Twelve Kizuki.

Incidentally, the "pretend family" was an act approved by Muzan, who deliberately gave demons the trait of cannibalism to prevent rebels from banding together. Muzan allowed Rui to gather demons under him because he saw Rui's childish desire for parental substitutes and his tendency to discard unsatisfactory replacements.

Techniques List:

Kokushirou: Encloses the opponent in web-like threads and cuts them.

Ayamekago: Traps the opponent in a narrower basket-like space than Kokushirou and finishes them off.

Kokushirinten: The hardest threads attack like a tornado, tearing the opponent to pieces.