Demon Slayer is a highly acclaimed and hugely popular anime that has been praised for its animation and characters. However, that does not mean that neither the characters nor the anime and manga collaborators have made mistakes throughout the series.
From Hashira who were unable to protect the innocent to a demon king who may not always make the best decisions, the characters in Demon Slayer are not perfect. Similarly, the author and directors of the anime and manga have also made mistakes that have raised eyebrows. Despite these mistakes, the anime has been largely successful and garnered fans from far and wide.
8 Muzan Is Probably Regretting Turning Nezuko
One of Muzan's greatest mistakes was his attack of the Kamado family and subsequent turning of Nezuko into a demon. It was a happy accident that Nezuko was both turned into a demon and could later walk in the sun — which was Muzan's goal all along.
Muzan did not expect this when he turned Nezuko and left her on the Kamado property for Tanjiro to find and save. This not only meant that the answer to Muzan's goal was in the other side's hands, but also that Tanjiro had a motive to kill Muzan.
7 Losing Rengoku So Quickly Felt Like A Disservice
Kyojuro Rengoku enthralled fans with his lovable personality and his impressive fighting spirit, which also impressed Akaza. However, his quick death during the Mugen Train Arc meant that fans were doomed to grieve their new beloved favorite.
While Rengoku's death served an end and was arguably necessary for the progression of Demon Slayer's plot, the quick nature of this event was the problem. Showrunners and the author made fans fall for him and then took him away; fans wanted a bit more time with him.
6 Muzan Also Probably Regrets Letting Tamayo Go
Tamayo was originally Muzan's follower, however unwilling, but after the fateful encounter between Yoriichi and Muzan, Tamayo was able to go off on her own. It is not that Muzan did not try to find and stop Tamayo, but she found a way to stay on the downlow.
Tamayo's later meeting with Tanjiro seemed pretty convenient. However, Tamayo's experiments with demon blood were integral to Tanjiro and Nezuko's pursuits. Though Muzan was bent on finding a way to walk in the sun, he alienated all those who would have achieved this for him and it kept haunting him.
5 Making Zenitsu's Power Only Available When Asleep Makes Him Unable To Participate
Zenitsu certainly has his character flaws, but his two most apparent are his obsession with women and his cowardice. However, that cowardice goes away when he is asleep and his sleep-self fights for him with impressive speed and power. While this is a cool gimmick at first, it quickly becomes more of a problem than a solution.
Zenitsu cannot grow stronger on his own (while awake). On top of that, the Demon Slayer anime and manga writers must always have a reason for him to be asleep to fight.
4 Muzan's Not Having The Top Demons Take Out All The Hashira Seems Like An Oversight
As Demon Slayer fans saw with Akaza, the top-tier demons are incredibly strong. Fans question why Muzan has not had them team up to fight the Hashira — especially when he is so desperate to kill Tanjiro. According to Enmu, Tanjiro's reputation preceded him, and Tanjiro's death had been ordered.
However, Enmu failed, as he was not strong enough, and Akaza, though able to kill Kyojuro, was unable to kill Tanjiro. If Muzan wanted Tanjiro or any one of the Hashira dead, he would have sent two top-level demons.
3 Having So Many Types Of Breathing Can Be Confusing
The power system found in Demon Slayer is a bit different than many shonen fans are used to. There are many different types of breathing styles that do not necessarily seem as if they would go together or section off easily.
This makes Demon Slayer fans wonder why Sun Breathing should be so different than Fire Breathing, other than to give Tanjiro a lineage that would make him a threat to the series' villain.
2 Having So Many Demon Slayers & Slayer Candidates Die Points Out Hypocrisy
The Hashira often do controversial things and they come across as harsh and unfeeling pretty regularly. They often send their underlings to their deaths, as was seen in the Natagumo Mountain Arc. Furthermore, the selection process to even become a Demon Slayer leads to a lot of unnecessary death.
This seems so contrary to Rengoku's claim that he would always save his underlings. It is not necessarily all the Hashiras' fault though — they too answer to someone else. Still, their methods and results seem problematic next to their goals and philosophies.
1 Having Tanjiro Unable To Decide His Breathing Style Makes Him Simultaneously Too Weak & Too Strong
Tanjiro's main attacks are part of the Water Breathing Style, as popularized by Sakonji Urokodaki and Giyu Tomioka. However, he also learns the Hinokami Kagura, which is a Sun Breathing move. It makes sense that he would try and learn Water Breathing since he was found by the Water Hashira.
However, as Kyojuro stated when he saw Tanjiro's black sword, those who wield a black Nichirin Blade often cannot decide which style of breathing they want to learn and die as a result. However, that often works to his advantage, which is also pretty convenient.