Demon Slayer established Muzan Kibutsuji's Twelve Kizuki as his main demon force. They are the main antagonists for the vast majority of the series and the biggest obstacle for Tanjiro Kamado and his friends. However, these demon entities were originally humans, which prompts the question of which one would have been the best as a member of the Corps.
It is an interesting question since the likes of Akaza and Kokushibo were already fighters before turning into demons, while the others perhaps had a stronger moral core that could have led them to be great Demon Slayers. Naturally, this depends on the audience's perspective, but also on the main requirement needed to become a member of this demon-hunting organization.
Disclaimer: This article contains spoilers from the manga/anime and reflects the writer's opinion.
Exploring which member of the Twelve Kizuki could have been the best Demon Slayer

Among the Twelve Kizuki, some members stand out as being regarded as among the best to hunt and eliminate demons, with Akaza arguably being the best example. Many fans have often theorized that he wasn't truly evil and that his tragic backstory pushed him to become a demon, which means that if he had managed to join the Corps, he perhaps would have been a stellar member because of his natural fighting skills.
Some have also pointed out how Akaza tends to fight with his fists, which is a rarity in the series, but there are examples among the Hashira, such as Kocho Shinobu and Gyomei Himejima, that don't use the traditional Nichirin to fight demons. Therefore, he could perhaps get special tools for his fists with that material to fight these creatures, which wouldn't be so out of place.
On the other hand, there is the character of Kokushibo, who not only shared blood with Yoriichi Tsugikuni as his brother but was an actual member of the Corps, so he is the most obvious choice. He is trained in breathing techniques, but was already quite powerful before turning into a demon, so he is considered one of the top choices to be considered as a Demon Slayer.
More details about this

The biggest question regarding the Twelve Kizuki in this discussion, barring the obvious choice of Kokushibo, is how each of these characters would react to becoming a Demon Slayer. That is because it will play a major role in their development, with the example of Douma serving as a counter-argument to some of them being simply too broken as humans to be a part of this organization.
There is the example of Daki and Gyutaro, who, at one point in their deaths, were mirrored to Tanjiro and Nezuko Kamado. This means that in this alternate scenario, they could have grown into forces who could do good to the world. It is difficult to predict since some characters were beyond redemption before turning into demons, so it depends on specific cases.
Final thoughts
When considering their lives, there is a good chance that Akaza and Kokushibo would be the ones best suited to be members of the Demon Slayer Corps. That is because of their motivations, abilities, and how, in this scenario, they would have managed to overcome the tragedies that pushed them to become demons.
Related articles:
- One Demon Slayer character was truly born to be a demon (& it's not Muzan)
- Tanjiro's inability to change this Demon Slayer character is one of Gotouge's best choices
- Jigoro's final act is one of Demon Slayer's most misunderstood plot points
- Tanjiro is not Demon Slayer's chosen one, and it only makes the story better