Since the beginning of Demon Slayer, one of the most contended plot points has centered around Nezuko’s age regression. Many fans believe that the decision to have Nezuko behave as childlike as she does post-transformation takes agency away from the only central female character of the series. Not only this but her childishness supposedly contrasts with the anime’s long-running themes.
However, the final installment of Season Three’s “Swordsmith Village” arc hinted at the reason behind Nezuko’s apparent immaturity. After transforming, most demons regain their sense of self, but instead of going down this typical route, it’s likely that Nezuko sacrificed her awareness in order to co-exist with humans. Instead of being a typical demon, she was able to change herself into a more passive member of the demographic.
Nezuko Has Suppressed Her Consciousness
Nezuko was only briefly featured as a human character, as very early in the series she was transformed into the demon fans recognize. However, even from this brief introduction to the character, it’s clear she was a mature child before becoming a demon. Despite being only 12, she was the second-born child in a large family, so was quick to take on her fair share of chores to help her parents. Frequently, she is pictured carrying or soothing smaller siblings, clearly taking on a maternal role at a young age.
However, after being transformed into a demon by Muzan Kibutsuji, the Demon King, she quickly regressed in mental age and maturity. No other demons have exhibited this same regression, making this mysterious experience unique to Nezuko. The final episode of season 3 finally brought to light why this may be.
The scientist, Lady Tamayo, has been studying Nezuko’s blood in hopes of finding a cure for demon transformation. While she is very close to ending the epidemic, Tamayo has also stumbled upon another conclusion while examining Nezuko’s ever-changing blood samples. She believes that the reason the young girl has never regained her consciousness is because there is something else taking priority in her mind– coexisting with humans. In short, Nezuko has decided to sacrifice her sense of self to change her biological makeup, no longer craving human blood to survive and instead fighting alongside humans in their battle against demons.
Nezuko Had a Unique Demon Transformation
After being transformed, Nezuko had a very different experience in her first moments as a demon. While most demons would awaken alone and confused with a sudden bloodlust for humans and no previous memories, Nezuko was removed from the original crime scene and taken care of by Tanjiro. She was unable to get an initial taste of blood as her brother carried her away from their family’s bodies and towards a doctor, so never got a taste of a demon’s main craving. This, of course, makes it far easier to resist than if she had gone on a rampage as many demons would have.
While Nezuko did wake up with the same violent instincts of a typical demon, attacking her brother in a blind rage, Tanjiro was once again there to hold her back until she regained her senses. Nezuko’s love for Tanjiro provided her with a very strong motivation to stay in her regressed state of consciousness for whatever period necessary. This contrasts with her fellow demons, who had no one to support them in the moments after their transformation. As such, they gave into the new instincts that ran rife through them and succumbed to the life of a demon. However, if they had similar support systems in place, their fates could have changed just as Nezuko changed her own.
Nezuko Can Sacrifice Her Conscience Because of Tanjiro’s Support
Unlike Nezuko, most demons did not have a very strong reason to force themselves not to eat after being transformed. Moreover, many of her counterparts had no respect for humanity to begin with, or everyone they loved had died, putting them in too much despair to put up a fight. As such, they had no reason to fight the lifestyle forced upon them and surrendered to the nature of a demon, as this was a better alternative to their experiences with humanity. For example, Gyutaro and Daki were treated poorly during their time as humans, with Daki even being brutally attacked and left to die in a ditch by a human. Thus, upon being transformed by Upper-Rank Doma, neither had any reason to oppose the change.
Meanwhile, Nezuko has been supported by Tanjiro from the moment she transformed. He has always been there to hold back her urges or protect her from demon slayers and has given her a reason to keep fighting for her humanity. She is a rare demon who had the protection of someone else, so could instead sleep to regain her energy and focus on changing her biology. Only Nezuko can afford to trade her sense of self away and to become so childlike, clueless, and defenseless because she had Tanjiro to constantly take care of her. Unlike other demons, she’s never had to exist on high alert and be forced to live with an all-for-one mentality.
Likewise, Nezuko is desperate to return to humanity because if she doesn’t, her brother will never stop fighting demons and putting his life at risk. Regaining consciousness and convincing him to quit for his own safety isn’t an option for her as the demon slayers wouldn’t let her live, and Tanjiro would never let her die. These siblings thrive off of one another and have always been solid support systems, which allow them to take such unique positions as demon and demon slayer.
While Nezuko’s age regression at first seems like a poor writing choice, it’s clear that this detail lines up unexpectedly with the anime’s central themes of love, family, and humanity. The Demon Slayer narrative has always suggested that nothing can break the bond between Nezuko and Tanjiro, and this recent discovery more than proves this theme. No other demon in the series has had the opportunity to sacrifice their consciousness because they never had anyone to rely on. Only the little sister who loves her older brother enough to achieve the impossible could make such a huge sacrifice and change her demon biology.