Rui's freedom in Demon Slayer speaks of Muzan having humanity left within him

Muzan is an irredeemably evil character from Demon Slayer. From the start of the series, he is portrayed as entirely self-centered and abusive toward his allies. Muzan's pattern of abuse was so terrible and compelling that even members of the Upper Kizuki, who could overpower him, didn’t consider taking action against him. Although he wasn’t always around his demons, he maintained a strong hold over their freedoms.

However, among all the demons in Demon Slayer, there was one who may have been favored by the demon lord: Rui. Rui was one of the antagonists of Demon Slayer's first season. While he wasn’t the strongest demon to ever exist, Muzan bent one of his most significant rules for him. The rule stated that Muzan did not permit his subordinates to turn other humans into demons.

Before Rui, only the strongest demons in the Twelve Kizuki were granted that privilege. Rui, a lower-ranked member of the Twelve Kizuki, was allowed to create his own family. This privilege may have stemmed from Muzan's deep understanding of Rui. The two characters shared a similar existence as humans. So, Muzan allowing him to have his family is evidence that the demon lord has a human side beneath all the evil.

Disclaimer: This article is a speculative theory and reflects the writer’s opinion.

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How Demon Slayer uses Rui to showcase Muzan’s human aspects

Muzan was a father figure to Rui in Demon Slayer (Image via Ufotable)

Muzan is one of anime’s best-written villains and a standout character from Demon Slayer. The key aspect that makes Muzan function so well as a villain is his propensity for evil. Every action he takes is directed toward malevolence. Whether through his verbal abuse of demons—his only allies—or the cruelty with which he kills humans, Muzan basks in evil.

However, there are also instances in Demon Slayer where viewers see Muzan displaying human qualities. This is evident in both his reactions and actions. A prime example of his most human reaction occurs when he discovers that Nezuko can withstand sunlight. Muzan appears peaceful and free from worry as he hears the news.

Muzan allowed Rui to turn humans into demons and rule over them (Image via Ufotable)

Another instance of Muzan’s action revealing his humanity is his treatment of Rui. Rui was the only demon with whom Muzan interacted without harshness. He treated Rui like a son. Some might argue that this was classic Muzan manipulation since he always knew the right words to use, but this situation was different.

If Rui were powerful, the notion of Muzan manipulating him would carry more weight. However, Rui was not really powerful, as the Hashira could easily defeat him. Muzan allowed a demon as powerless as Rui to propagate other demons because he empathized with him.

Rui and Muzan had similar upbringings. Both were sickly children, and they became demons to overcome the looming sickness that held them back. However, there is a slight difference between them: Muzan became a demon as an adult, while Rui became one as a child. This might explain why Muzan views Rui as a son or brother.

Their similarities might clarify Muzan’s leniency toward Rui. Although Rui did not offer Muzan any direct value, he was permitted to form the Spider Family. He was also given Muzan’s blood and allowed to share it freely. Additionally, Rui’s status as a member of the Twelve Kizuki meant that he never changed his position despite being a lower-ranked member. He remained content with his rank and continued to receive support from Muzan.

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Final thoughts

Rui inherits many traits from Muzan once he becomes a demon. He uses violence to keep his family in line and manipulates family members when necessary. The main difference between him and Muzan is that he genuinely cares about others. In contrast, Muzan is self-centered; even though he treats Rui like family, he would abandon him to save himself.

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