Rui was a powerful demon who served as Lower Rank Five of the Twelve Kizuki under Muzan Kibutsuji. He was the central antagonist of the Mount Natagumo Arc and is best known for his obsession with "family," which he sought to recreate in his own twisted image by forcefully turning other demons into roles like Mother, Father, and Siblings.
Despite his youthful appearance and soft demeanor, Rui was one of the most sadistic and emotionally complex demons encountered early in the series. He embodied themes of broken familial bonds, loneliness, and the desperate search for connection.
Appearance[]
Rui appeared as a pale-skinned, white-haired boy with bright red irises and pale turquoise pupils, resembling a porcelain doll. His face bore a spider-like marking, with thin red lines stretching from his eyes and covering parts of his body like a web. He wore a white kimono with a spider web motif.
Before becoming a demon, Rui was a sickly child with frail limbs, bedridden most of his life due to a severe illness. His transformation into a demon restored his health but at a terrible cost.
Personality[]
Rui was emotionally stunted, obsessive, and deeply controlling, especially regarding his self-created "family." He demanded absolute obedience and loyalty, punishing any perceived betrayal with cruelty or death. Despite his cruel actions, Rui was not inherently evil — he was broken, having been transformed into a demon as a sickly child and manipulated by Muzan into believing that pain, fear, and submission equated to familial bonds.
His desire for a real family stemmed from emotional isolation and the trauma of killing his human parents after they attempted to end his suffering (and their own) out of love. Rui interpreted this act as betrayal, burying the guilt deep inside and trying to replace those feelings with artificial connections.
Despite his delusions, Rui longed to experience genuine love, and the encounter with Tanjiro and Nezuko — a brother and sister truly devoted to each other — deeply impacted him in his final moments.
Story[]
Mount Natagumo Arc[]
Rui lived on Mount Natagumo, where he created a fabricated demon "family" using fear and manipulation. Each member had a role — Mother, Father, Brother, and Sister — all forced to abide by his concept of familial hierarchy. He used threats, torture, and punishment to enforce "love," punishing anyone who failed to uphold his twisted ideal.
When Tanjiro Kamado and his group arrived at the mountain, they encountered terrifying spider demons controlled by Rui’s threads, including the traumatized "Mother" demon and a brutish "Father." Rui watched with eerie detachment as battles unfolded, taking particular interest in Nezuko, whom he believed embodied the sibling bond he longed for.
Rui attempted to force Nezuko into becoming his "sister", going so far as to threaten Tanjiro’s life to claim her. This led to a fierce confrontation where Rui's cruelty and Tanjiro's love for Nezuko clashed directly.
During the battle, Rui’s Blood Demon Art proved nearly fatal, but Tanjiro awakened his Hinokami Kagura (Sun Breathing), pushing Rui to his limits. In a heart-wrenching moment, Nezuko unleashed her Blood Demon Art: Exploding Blood to assist her brother, allowing them to nearly behead Rui.
However, Rui decapitated himself early using his own threads to avoid death, revealing the cunning behind his childlike demeanor. He was ultimately defeated when Giyu Tomioka, the Water Hashira, arrived and swiftly killed him with his Eleventh Form.
Final Moments[]
As Rui disintegrated, he reflected on his human life, remembering that his parents tried to kill him to free him from his suffering and join him in death. He realized that they had truly loved him, and his rejection of them had caused his greatest pain.
He wept in his final moments, yearning to apologize, and imagined reuniting with his parents in the afterlife. This moment of raw emotion added profound depth to his character, showing that beneath the monster was a broken child, craving love.
Powers and Abilities[]
Blood Demon Art: Cutting Thread Cage[]
Rui's Blood Demon Art allowed him to manipulate razor-sharp threads created from his own cells, strong enough to slice through flesh, bone, and even Nichirin swords.
- Thread Manipulation: He could control webs like marionette strings, binding, cutting, or shredding his targets from afar.
- Thread Cage: Rui could create a dome of threads around an enemy, slicing them from all angles if they didn’t escape or counter in time.
- Thread Strengthening: When in danger, Rui could strengthen his threads using more of his cells, increasing their sharpness and tension exponentially.
Thread Decapitation Technique[]
Rui could cut off his own head using his threads to avoid being killed by a Demon Slayer’s blade. This deceptive tactic made it incredibly difficult to kill him through traditional methods.
Enhanced Strength and Speed[]
Rui was far stronger and faster than ordinary demons, being a member of the Twelve Kizuki. He could casually hold enemies in place with threads or crush rocks.
Durability and Regeneration[]
He possessed high-speed regeneration, able to recover from most injuries instantly. Only decapitation via a Nichirin blade could kill him.