<p>Ever since Muzan was turned into a demon in the Heian era, he was always seeking a cure to protect himself from sunlight. The demon king was almost immortal, and have nearly no weaknesses or vulnerabilities. He can't even be killed after beheading.</p>
<blockquote class="spoiler">
<p>  The demon king cannot be killed even if his head was lopped off, as shown at the end of the Hashira training arc, season 4, where Gyomei Himejima chopped off his head. Muzan regenerated his head almost immediately.</p>
</blockquote>
<p>Thus, the only thing that can kill him is exposure to sunlight. If he is also immune to sunlight, then he would be truly immortal. There are only two known methods that can possibly let him be immune to sunlight: devouring/absorbing another demon that managed to be immune to sunlight, or find the blue spider lily. For the first possibility, Muzan created scores and scores of demons in hopes that one day one of them will be immune. For the second possibility, Muzan created the twelve kizuki (twelve blood moons) to aid him in combat as well as in finding the lily. The twelve kizuki is divided into upper and lower ranks, each consisting of six members. Most of the lower rank moons have little screen time, with the exception of Enmu and Rui. In comparison, the upper ranks have quite a lot of screen time, appearing in almost all arcs. Apparently, Muzan trusts the Upper ranks much, much more than the lower ranks. He also needed them because of the reason stated above. When one member dies, he finds another demon he deems competent enough to be a upper moon and let them fill in the gap. These demons must be really useful and helpful to him personally, and one that garners sufficient trust and respect from Muzan. Such is the case of Nakime, where Muzan is seen profusely complementing her due to her usefulness and competence.</p>
<blockquote class="spoiler">
<p> Thus, it is very understandable that Muzan let Nakime replace Hantengu as Upper four.</p>
</blockquote>

CC BY-SA 4.0
2024-08-10T07:41:59.977Z
2024-08-10T07:41:59.977Z
Ghibli Fan 007
<p>So, the MOON DEMONS are the demons that took an important amount of MUZAN's direct blood and didn't die, they were able to gain power and develop special demon techniques (like the Breath styles but demon way) through his power and they also took parts from his memory. And normal demons are just people who got bitten or were in cotact with demon blood and turned to demons.</p>

CC BY-SA 4.0
2024-06-04T14:42:31.290Z
And what make them replaceable?
Fumikage Tokoyami
CC BY-SA 4.0
2024-06-09T06:09:33.380Z
As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2024-06-04T13:39:45.813Z
2024-06-04T13:39:45.813Z
Hind Bhr
<p>The Upper Moons are replaced through deadly battles. The Upper Moon demons have lived a long time, eaten many people, and are very powerful, earning Muzan's trust more than the Lower Moons and receiving more of his blood. In other words, a demon who receives a lot of Muzan's blood and continues to eat people without dying will grow in power to the level of the Upper Moons. For example, Enmu from the Mugen Train arc: if he hadn't fought the protagonists directly but had continued eating people elsewhere, he might have become as strong as Daki in a hundred years.</p>

CC BY-SA 4.0
2024-07-12T07:43:16.803Z
2024-07-12T13:21:56.360Z
2024-07-12T13:21:56.360Z
夜凪静
<p>During the Hashira Training arc of <em>Demon Slayer</em>, we find out that:</p>
<blockquote class="spoiler">
<p> <a href="https://kimetsu-no-yaiba.fandom.com/wiki/nakime" rel="nofollow noreferrer">Nakime</a> has replaced <a href="https://kimetsu-no-yaiba.fandom.com/wiki/Hantengu" rel="nofollow noreferrer">Hantengu</a> as the Upper Demon four</p>
</blockquote>
<p>Even in final arc, Upper Demon Six will be replaced (not adding details for spoiler reason). So, why are Upper Moon Demon replaced if one of the member dies? As we know, <a href="https://anime.stackexchange.com/questions/66752/why-did-muzan-kill-the-lower-demon-moons">Muzan is very ruthless and wiped out the entire Lower Moon Demon due to incompetence</a>. How does the ranking system work for upper moon demons?</p>
<p><sub><strong>Note</strong>: Please add spoilers in your answer wherever possible</sub></p>

CC BY-SA 4.0
2024-06-10T20:56:24.210Z
"not adding details for spoiler reason" - proceeds to add another spoiler in question. Jokes aside, it's possible they were much stronger than Upper Five (don't remember if they were alive or not at season end).
DaemonsMercy
CC BY-SA 4.0
2024-06-18T12:39:23.680Z
I dont understand your question, why not? Hashiras are also replaced. If a commander dies in a military, he's also replaced. Makes sense
Pablo
CC BY-SA 4.0
2024-06-18T15:11:18.977Z
Hashiras can be replaced but demons are different. Muzan prefers order and reliance. If he sees incompetence, he kills them (unless they are already killed). So, you are saying that demons will be in a pack of 6(in each group) and they will be replaced if killed and not gradually reduce? Has anywhere in the Manga were this implied? @Pablo
Fumikage Tokoyami
CC BY-SA 4.0
2024-06-18T15:13:53.783Z
Or the alternative way of saying this is why Muzan prefers the upper demon over the lower demons?
Fumikage Tokoyami
CC BY-SA 4.0
2024-06-18T15:29:20.903Z
I've finished the Demon Slayer manga, but I dont recall all the details, that's why I didnt answer. But I think it's mentioned upper demons are replaced if killed. This isnt a spoiler because I'm not sure
Pablo
<demon-slayer>
Why are Upper Moon Demons replaceable in Demon Slayer?
# Why are Upper Moon Demons replaceable in Demon Slayer?
Posted by: username_0 on 2024-06-04
During the Hashira Training arc of *Demon Slayer*, we find out that:

> [Nakime](https://kimetsu-no-yaiba.fandom.com/wiki/nakime) has replaced [Hantengu](https://kimetsu-no-yaiba.fandom.com/wiki/Hantengu) as the Upper Demon four

Even in final arc, Upper Demon Six will be replaced (not adding details for spoiler reason). So, why are Upper Moon Demon replaced if one of the member dies? As we know, [Muzan is very ruthless and wiped out the entire Lower Moon Demon due to incompetence](https://anime.stackexchange.com/questions/66752/why-did-muzan-kill-the-lower-demon-moons). How does the ranking system work for upper moon demons?

**Note**: Please add spoilers in your answer wherever possible
**Tags:** demon-slayer
> **Comments:**
> **username_1**: "not adding details for spoiler reason" - proceeds to add another spoiler in question. Jokes aside, it's possible they were much stronger than Upper Five (don't remember if they were alive or not at season end).  
> **username_2**: I dont understand your question, why not? Hashiras are also replaced. If a commander dies in a military, he's also replaced. Makes sense  
> **username_0**: Hashiras can be replaced but demons are different. Muzan prefers order and reliance. If he sees incompetence, he kills them (unless they are already killed). So, you are saying that demons will be in a pack of 6(in each group) and they will be replaced if killed and not gradually reduce? Has anywhere in the Manga were this implied? @Pablo  
> **username_0**: Or the alternative way of saying this is why Muzan prefers the upper demon over the lower demons?  
> **username_2**: I've finished the Demon Slayer manga, but I dont recall all the details, that's why I didnt answer. But I think it's mentioned upper demons are replaced if killed. This isnt a spoiler because I'm not sure  
---
## 3 answers
### Answer by username_3 on 2024-08-10. Score: 2 | Accepted answer
Ever since Muzan was turned into a demon in the Heian era, he was always seeking a cure to protect himself from sunlight. The demon king was almost immortal, and have nearly no weaknesses or vulnerabilities. He can't even be killed after beheading.

> The demon king cannot be killed even if his head was lopped off, as shown at the end of the Hashira training arc, season 4, where Gyomei Himejima chopped off his head. Muzan regenerated his head almost immediately.

Thus, the only thing that can kill him is exposure to sunlight. If he is also immune to sunlight, then he would be truly immortal. There are only two known methods that can possibly let him be immune to sunlight: devouring/absorbing another demon that managed to be immune to sunlight, or find the blue spider lily. For the first possibility, Muzan created scores and scores of demons in hopes that one day one of them will be immune. For the second possibility, Muzan created the twelve kizuki (twelve blood moons) to aid him in combat as well as in finding the lily. The twelve kizuki is divided into upper and lower ranks, each consisting of six members. Most of the lower rank moons have little screen time, with the exception of Enmu and Rui. In comparison, the upper ranks have quite a lot of screen time, appearing in almost all arcs. Apparently, Muzan trusts the Upper ranks much, much more than the lower ranks. He also needed them because of the reason stated above. When one member dies, he finds another demon he deems competent enough to be a upper moon and let them fill in the gap. These demons must be really useful and helpful to him personally, and one that garners sufficient trust and respect from Muzan. Such is the case of Nakime, where Muzan is seen profusely complementing her due to her usefulness and competence.

> Thus, it is very understandable that Muzan let Nakime replace Hantengu as Upper four.
---
### Answer by username_4 on 2024-06-04. Score: -1
So, the MOON DEMONS are the demons that took an important amount of MUZAN's direct blood and didn't die, they were able to gain power and develop special demon techniques (like the Breath styles but demon way) through his power and they also took parts from his memory. And normal demons are just people who got bitten or were in cotact with demon blood and turned to demons.
> **Comments:**
> **username_0** (2024-06-04): And what make them replaceable?  
> **username_5** (2024-06-09): As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  
---
### Answer by username_6 on 2024-07-12. Score: -1
The Upper Moons are replaced through deadly battles. The Upper Moon demons have lived a long time, eaten many people, and are very powerful, earning Muzan's trust more than the Lower Moons and receiving more of his blood. In other words, a demon who receives a lot of Muzan's blood and continues to eat people without dying will grow in power to the level of the Upper Moons. For example, Enmu from the Mugen Train arc: if he hadn't fought the protagonists directly but had continued eating people elsewhere, he might have become as strong as Daki in a hundred years.
---
