You thought that you defeated me? You sad fool. Were you happy with your delusions?
Japanese Voice Actor: Koki Uchimaya
English Voice Actor: Billy Kametz
Age: 13 (Physically)
Manga Debut: Chapter 29
Anime Debut: Episode 15
Rui was born with a sickly body. He is frail and he easily gets stressed. His body would get tired by simply walking and breathing. Being born from an affluent family, he is well taken care of. His mother and father would take care of him and loved him deeply even when he is always sick.
One day, he suddenly got better. He suddenly has a strong body and his parents got happy about it. He got well because Muzan Kibutsuji offered to save him.
Being a demon he would need food and this is in the form of eating humans. This resulted in him killing a man in their home. His parents discovered the gruesome scene and they got scared of him. His parents decided that night that they would kill him. They would wait for him to sleep and they would kill him so he would not do anything gruesome in the future.
When Rui fell asleep his father sneaked into his bedroom armed with a knife and told Rui not to worry as he will kill himself as soon as he had killed him. His mother was crying outside the door as his father is attempting to kill him.
Rui woke up during the attempt on his life. He got angry with them and killed them to defend his life. After killing both of them, he was in denial and told himself that those he killed are his fake parents and the real ones will never do anything like that.
While his mother was lying, she apologized to him saying that she is sorry for not being able to give him a healthy body. Upon hearing this, he remember the last words of his father that they would kill themselves as soon as they killed him.
Rui realized that his parents loved him and they do not want him to become a demon. Rui was in emotional turmoil. Muzan however, encouraged him that those he killed are not his real family because they did not support him. Muzan even supported him in his early stages as a demon and told him to look for a new family.
Rui as a Demon
After Rui became a demon, he was out killing and eating humans. He grew stronger and later, he was acknowledged by Muzan and he became a member of the 12 Kizuki. He became the Lower Moon 5. Rui then started establishing his family.
One time he met a demon who was running for her life because she is being chased by a group of demon slayers. He offered to save her if she becomes a member of his family. For her to survive she agreed with him. Rui eliminated the group of demon slayers.
Rui gave the demon a drop of his blood to give her power. He also altered her appearance to match his. He then acknowledge her as a member of his family and called her the older sister. When the Older Sister attempted to run away from her family, one of the sister demons told Rui. He got enraged by her attempt and stopped her from doing so. He then beat her and he string her up to burn under the sun.
When Kyogai was remembering that he wanted to return to the ranks of the Kizuki, he remembers Rui. Then the group of Tanjiro went to Natagumo Mountain to hunt demons. Rui saw him, Murata, and Inosuke as he walks on threads connected among trees.
As the mother demon is fighting the demon slayers, Rui went to her and ask her how long would it take for her to finish. The mother said she will finish shortly. Rui threatened to tell the father demon if she would not finish as soon as possible. The mother begged her to not tell his father and she would finish immediately.
After Tanjiro had a clash with the father demon, he heard a scream. It turns out that Rui is lashing at the sister demon. Rui told Tanjiro not to interfere as they are a family connected by a special bond. While Tanjiro and Rui were arguing over Rui’s bond with his family, they were interrupted by another demon slayer that was shredded by Rui.
Rui then turned his attention back to Tanjiro and started attacking him. He told Tanjiro that he would not immediately kill him but would dissect him. When Tanjiro is about to strike Rui with a breathing style, his blade broke.
Tanjiro was not able to strike back but he just keep on dodging so he would not get injured. When Tanjiro was not able to dodge a large web that descended on him, Nezuko protected him. Rui offered Tanjiro that he will spare his life in exchange for Nezuko.
Rui said he wanted Nezuko to be his little sister instead of Tanjiro. The fight ensued between Tanjiro and Rui, and for the first time, Tanjiro was able to use Hinokami Kagura and he was able to slice through Rui’s threads.
After using Hinokami Kagura, Rui had to behead himself to avoid being killed by Tanjiro. He got angry and decided to just kill Tanjiro. When he was about to attack Tanjiro, Giyu arrived and stopped his attack.
After being stopped by Giyu, Rui called demons slayers insignificant insects and used his most powerful technique to get rid of him. Giyu used the eleventh form of Water Breathing, stopping all the attacks of Rui and eventually killing him.
Rui has pale skin. His face has the same pale skin with red dots. His hair has the same resemblance as the legs of the spider and is pink in color. The sclera of his eyes are red but his irises are pale blue.
Being part of the 12 Kizuki he has an engraving on his left eye of Kagen (Lower Rank) and Go (Five). He wears a kimono with a spider web pattern.
Rui is always calm. He does not call demons or humans names or insult them. Even when he was angry with Tanjiro he still maintains the same tone of voice. His near guttural tone is the only implication that he is getting irritated or angry.
He has a twisted belief of what a family should be. This kind of belief had him kill even members of his family who are trying to escape. He can be authoritarian and cruel to his subordinates. He wanted his rules to be followed to the dot.
He can act mightily and even for his fellow demons, he has the attitude of looking down on them. The delusion of Rui of what a family should be could lead him to treat cruelly.
Rui is undoubtedly one of the strongest demons. He was able to control a bunch of demons in the Natagumo Mountains. He was even able to capture and coerce them into working for him.
Rui could easily overpower the likes of Tanjiro and kill several demon slayers with ease. Rui has the same power if not stronger than Enmu, who is the Lower Rank 1 during that time. The Blood Demon Art of Rui is one of the strongest.
He can do cell manipulation as he can alter the appearance of other demons to be the same as his. Having family members, Rui had to distribute his power to other members of his family. This had weakened him and he could no longer have a decent fight with Giyu. Even during the death of his family, he was not able to retrieve the powers he bestowed on them.
Rui brags that his body is more durable than the thread he created. Like a spider, he can easily manipulate threads that are the same as a spider web. He can use it to trap opponents, hang them and even kill them using his thread.