The overall quality of Demon Slayer has blown away many anime fans. The series has taken fight scene animation to a whole new level. These thrilling fight scenes are complemented by fantastic characters that the audience wants to see succeed. Such dynamic characters have drawn fans in with their unique personalities and depth. However, despite all of the good that exists within Demon Slayer, the series is not perfect.
Nezuko Kamado represents Demon Slayer's biggest issue. Nezuko is arguably the most important character in the series. Her transformation into a demon is the reason why Tanjiro decided to join the Demon Slayer Corps. His goal to turn her back into a human is his primary motivation to risk his life fighting demons. Despite this importance to the plot and how she drives it forward, Nezuko lacks the same depth of characterization as her peers.
Nezuko Contradicts Demon Slayer's Themes
One of the most important themes in Demon Slayer is humanity. It is consistently reinforced that people who are turned into demons still have a part of their humanity inside of them. They aren't mindless monsters with no self-control. They still maintain their personality, wants, ambitions and compassion for others. The series recognizes them as fully-fledged characters that are just as complicated and layered as any other human, but Nezuko isn't treated the same way.
All of the complexity and depth that exists for demons isn't present for Nezuko. It seems like turning into a demon simplified her character instead of expanding it. Nezuko doesn't have any desires or goals of her own. Her character isn't given any real agency. She does whatever Tanjiro tells her to do without question, and the only time she acts independently is when she needs to save another person's life. One of the reasons why she is so protective of other people is because she was hypnotized to act that way by Urokodaki. It wasn't a choice she made.
Nezuko behaves more like a well-trained pet than a real person, which creates a problem in the narrative. Tanjiro and others believe that Nezuko is worth saving because she has held onto her humanity, but she has shown a lower level of human-like qualities than demons that have killed dozens of humans. Nezuko is nice to other people and will fight to the death to protect human life, but she doesn't act like her own person.
Humanity Has Been Stripped From Nezuko
When Nezuko became a demon, it seems like the series did everything in its power to stop her from being a full character. The biggest sign of this is her bamboo muzzle that prevents her from speaking. The muzzle is entirely unnecessary. She has proven before that she can restrain herself in the presence of human blood. Even if she couldn't, Nezuko has superhuman strength and has kicked holes in buildings. She can easily remove the muzzle herself if she wanted to. The only purpose the muzzle serves is to hamper her ability to speak.
There are other forms of communication besides speaking, but Nezuko doesn't use any of them. It seems like she doesn't even have thoughts at times. Other characters are given inner monologues so that the audience knows what they're thinking or feeling. Nezuko isn't even given that much characterization. The only inner monologue she is ever given is the ideas that Urokodaki hypnotized her to believe. She has yet to indicate that she even wants to be human again. The entire series revolves around this idea, yet the audience can't say for sure that it's something she herself wants.
Nezuko spends most of the series sleeping inside the box that Tanjiro carries on his back. The sun does pose a threat to her and she does need to sleep for long periods to regain her energy since she can't eat people, so it would make sense that she stays in the box. That being said, Nezuko is in the box even when she doesn't need to be. When it's night or when they're inside and away from the sun, Nezuko still stays in the box. The only time she ever really leaves it is when Tanjiro needs her to fight. This makes her more of a weapon than a person, as her primary interaction with the world is via combat.
Although she is only a year younger than Tanjiro, Nezuko behaves like a toddler. This is strange since she was much more mature before she was a demon, and other demons didn't regress when they were transformed. When she's not fighting, Nezuko often acts very absentmindedly, which is different from the responsible older sister she was before. Other characters also treat her like an infant, even though she should have around the same level of maturity as Tanjiro, Zenitsu or Inosuke. The fact that, when she shrinks, she appears younger doesn't help either.
Nezuko Doesn't Have to Be This Way
All the barriers that prevent Nezuko from being a full character also stop her from forming meaningful bonds with others. Nezuko is close with her brother but with almost no other characters. She doesn't communicate with anyone, and the fact that she is always in the box means that she is rarely in the company of others. Even when she is around other people, the fact that she has the mindset of a toddler means that the relationship is in no way equal. All of Nezuko's relationships are very one-sided.
There's nothing in the narrative forcing Nezuko to be this way. There are plenty of other characters that share the same qualities as her but still can be full characters. Tamayo and Yushiro are good demons that protect humans, but they don't have to wear gags that stop them from speaking. Rui is a demon that looks like a child but still has a level of maturity appropriate for his age. Even Kanao, who rarely spoke and needed other people to tell her what to do, eventually gained her own agency. She's now making choices for herself, even if those choices are opposed to her superiors.
If Nezuko had more of a personality and will of her own, it would only make the story better. It would make Tanjiro's goals more meaningful since he would be fighting for a real person the audience could connect to instead of the blank slate that is his sister. It would also change Nezuko from a loyal pet or useful weapon into an interesting character with genuine depth. The story of Demon Slayer is mostly about Nezuko, but she is treated more like an objective than an active player in her own life.
