Upper Moons Are Based On Diseases?!

Updated June 1, 2023 by Noel Vermen

The Upper Moons are the strongest demons in Kimetsu no Yaiba. What if I tell you that these deadly beings are based on real-life diseases? However, before we dive into it, I must warn you that there will be spoilers ahead! Also, if you’re looking for more Demon Slayer content, you can check out the strongest demons in Demon Slayer!

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UPPER MOONS ARE BASED ON REAL-LIFE ILLNESS?!

Upper Moon Six: Daki and Gyutaro

In the Entertainment District arc, when Tanjiro and the demon slayers finally defeated the demon siblings, Gyutaro remembered his sister’s name. (Entertainment District Arc Episode 11)

He mentioned in Chapter 96 that Ume was named after the disease that killed their mother. This disease might be syphilis – a sexually transmitted infection.

This is likely the reason why Gyutaro mentioned that the names “Daki” and “Ume” were terrible. Daki not only means Fallen Princes, but it can also refer to “dispose of” or “abandon.” (Manga Chapter 96)

While “Ume” is used in the word for “syphilis” and is written using the characters for “plum” and “poison.”

If Gyutaro’s mother had an STD, it is possible that he was born with congenital syphilis.

This happens when a pregnant woman with syphilis passes the infection to her baby, which can lead to bone deformities, yellowing of the eyes, skin rashes, and underdeveloped teeth.

With all this evidence, it seems that Daki and Gyutaro are genuinely derived from syphilis.

New Upper Moon Six: Kaigaku

Now that there is a vacancy in the Upper Moon Six, Kaigaku will fill the position and take the spotlight, performing his role during the Infinity Castle arc.

Kaigaku joined the Demon Slayer Corps and was actually a senpai of Zenitsu Agatsuma.

However, when the Upper-Rank One Kokushibo beat his ass! In a desperate attempt to save his own life, Kaigaku begged Kokushibo to turn him into a demon. (Manga Chapter 145)

Zenitsu explained to Kaigaku that when their master, Jigoro Kuwajima, heard the tragic news, he was overwhelmed with grief and could not bear the shame, so he committed seppuku. (Manga Chapter 144)

Yet, Kaigaku is an a-hole and didn’t give a shit, so he and Zenitsu had a heated battle. (Manga Chapter 144)

Although Zenitsu may have only honed one skill, he defeated Kaigaku with just one strike. And that was it – he was out of the game. (Manga Chapter 145)

Soooo… what might be the inspiration behind his character design?

Most fans are saying Kaigaku might be inspired by rabies because his mouth looks like a dog. (Manga Chapter 143)

According to the theory, Kaigaku’s powers may have been inspired by hyperkeratotic scabies, which is a severe type of scabies that can cause cracks in the skin. (Manga Chapter 145)

Kaigaku’s Blood Demon Art has a similar effect, which could be the reason why Zenitsu’s face cracked open while fighting him. (Manga Chapter 146)

Upper Moon Five: Gyokko

Now, let’s move on to the Upper Moon Five: Gyokko.

Gyokko refers to himself as an artist, and in the Swordsmith Village Arc, we’ve witnessed how he morbidly expresses it. (Manga Chapter 111)

Aside from his twisted love for his so-called “art,” Gyokko’s powers are all related to themes involving water and fish.

His Blood Demon Art might be inspired by amoebic dysentery – an intestinal infection caused by a microscopic parasite. This illness is mostly caught by drinking contaminated water or eating infected seafood.

This inspiration may have led to his “water bending-like” skills and those creepy-looking sushis. (Manga Chapter 112)

Speaking of sushi, did you know that we’ve put a lot of effort into creating a step-by-step guide on how to draw sushi?

Gyokko may have had impressive powers and skills, but in Chapter 121, Tokito manages to defeat him.

Upper Moon Four: Hantengu

Also, in the Sword Smith Village Arc, Gyokko was assisted by Hantengu, who may seem cowardly at first but dude, this guy just surprised us with his abilities. (Sword Smith Village Arc: Episode 1)

In the manga despite having his head chopped off multiple times by the demon slayers, Hantengu survives by splitting himself into more demons. (Manga Chapter 107)

Hantengu’s appearance and characteristics, such as the large lump on his forehead, disfigurement, and discolored skin, may suggest that he was inspired by leprosy. (Manga Chapter 106)

However, not all of his forms exhibit these symptoms. 

New Upper Moon Four: Nakime

After Hantengu is defeated in Chapter 125. Nakime rises through the ranks to take his place as the new Upper Moon Four. 

With her ability to control the fortress and transport other demons using her Biwa, Nakime is a valuable asset to the demons, especially during the battle at the Infinity Castle arc. 

In Chapter 164, I agree with Iguro when he said that Nakime’s ability is annoying, but I disagree with him when he said that it’s not that “deadly.”

Just take a look at how Nakime merely crushed Mitsuri and Tokito! (Manga Chapter 164)

After knowing that, I would like to say that the meaning of her name perfectly fits her character. 

This is because I’ve found out that Nakime’s name means “Naki,” which can be translated to “to call” or “to cry,” and “Me,” which means “woman.”

Therefore, her name can be interpreted as a “woman who calls,” which perfectly suits her role as a lady who summons and transports other demons. Now that got me thinking who do you think is the strongest female character in Demon Slayer?

In theory, Nakime might be inspired by pink eye, an infection that turns the white part of your eye red or pink and makes your eyes itchy, gooey, and blurry.

However, even if she does have these symptoms, they don’t seem to affect her abilities at all!

In Chapter 134 during the Hashira training arc, Nakime used her eyes to spy on the Demon Slayers, and in Chapter 136, she even managed to locate the hidden mansion of Kagaya Ubuyashiki.

While the theory of Nakime being inspired by pink eye is intriguing, there isn’t much evidence to support it. 

Upper Moon Three: Akaza

So, let’s move on to another Upper Moon demon, Akaza!

Akaza first appeared in the “Infinity Train” movie, which featured one of the best and coolest fight scenes we have ever witnessed, but also one of the most heartbreaking one so far.

I know we all hated Akaza for what he did to Rengoku, but his backstory is actually one of the saddest in the series.

During the Infinity Castle Arc, when Tanjiro and Giyu successfully beheaded Akaza, he didn’t die. However, as he still desired to fight, a girl intervened, and Akaza’s memories were revealed. (Manga Chapter 153)

We learned about his motives for getting stronger, his father’s tragic death, the significance of his tattoos, his mentor’s teachings, and his love for a suffering girl.

These memories and emotions led him to take his own life. Now, he’s home, reunited with his father, his master, and his loved one. (Manga Chapter 157)

Now, let’s hit the theory! Akaza is probably based on Measles because, in Japan, measles was also called “aka-mogasa,” which contains the same characters in Akaza’s name.

“aka-mogasa” actually means “red smallpox.” But back in the day, people in Japan would use the same term to describe both measles and smallpox, so it could get a bit confusing.

They started calling measles “red smallpox” during the Edo period which connects in Chapter 154 when Keizo mentioned that Akaza was from Edo. 

Oh, by the way, did you know that Doma mentioned that Akaza doesn’t eat girls? (Manga Chapter 157)

The reason for this is presumably because of his fiance, Koyuki. (Manga Chapter 155)

Upper Moon Two: Doma

Well, speak of the devil! Let’s go over Upper Moon Two: Doma. 

Doma might look charming with those fancy eyes and his phony nature, yet we all know the truth! This dude is ruthless! Hmm… He might be ruthless but who do you think is the strongest character in Demon Slayer?

We witnessed his strength during the Infinity Castle Arc, and it opened up another wound in our hearts. He killed Shinobu! This guy absorbed her body! (Manga Chapter 143)

I might forgive Akaza, but Doma? No way, bro! I’m not forgiving him!

Don’t forget that he’s responsible not only for Shinobu’s death but also for Kanae Kocho! That’s why Shinobu seeks revenge! (Manga Chapter 141)

Now, she has found Doma, and as our Insect Hashira battled him, we witnessed the effect of Doma’s Blood Demon Art, which could connect to our theory. (Manga Chapter 141)

Doma may be based on tuberculosis, which is a bacterial infection that affects the lungs, as well as other organs like the kidneys, spine, and brain.

In Chapter 159, Kanao warned Inosuke not to breathe the cold air. Why? Because Doma’s Blood Demon Art is cryokinesis, which can cause severe damage to those who inhale it! This has a similar effect to tuberculosis.

 As Kanao and Inosuke faced Doma, he grabbed Inosuke’s mask and saw his face, which reminded Doma of someone… (Manga Chapter 159)

Someone that looks exactly like Inosuke… and it was revealed that it was his mother! This MOFO killed Inosuke’s mother! (Manga Chapter 160)

Fate has a peculiar way of orchestrating revenge.

Kanao saw her sister die and Inosuke found out who killed his mom. You know what that means, right? It’s payback time, baby!

As soon as Doma was leaving the battlefield, Shinobu’s poison kicked in! (Manga Chapter 161)

Chapter 162 revealed a conversation between Shinobu and Kanao where they mentioned that the final form of Flower Breathing, Equinoctial Vermilion Eye, can cause blindness to the user.

This could be related to the theory that the effect of Flower Breathing’s final form is similar to the side effects of a drug used to fight tuberculosis called Ethambutol.

So, with this technique Kanao and Inosuke successfully defeated Doma! (Manga Chapter 162)

Now, here’s a funny thing… when Doma and Shinobu met in the afterlife, it seems that Doma regained his feelings and even asked Shinobu if she wanna go with him, and he gets instantly rejected! (Manga Chapter 163)

As we laugh at Doma’s romantic dreams crushed underneath Shinobu’s heel or should I say Inosuke’s feet? 

Upper Moon One: Kokushibo

Let’s move on to Upper Moon One: Kokushibo.

Before we further discuss the theory about this bad boy, let me give you a slight taste of what happened in the manga. 

In Chapter 165, Tokito mentioned that Kokushibo is on a different level and his presence alone made him tremble for the first time.

We have also learned that Tokito and Kokushibo are related. (Manga Chapter 165)

However, Kokushibo displayed his ruthless behavior towards his own kin. He not only chopped off Tokito’s arm but also impaled him. He even offered Tokito the chance to become a demon. (Manga Chapter 165)

Then Genya stepped in, but Kokushibo quickly butchered him! (Manga Chapter 166)

Now Sanemi tries to save his little brother, and he actually puts up a great fight! However, this demon is too much for him to handle alone. (Manga Chapter 168)

Then Gyomei enters the fray! And what happens next? Genya and the three Hashiras fought the strongest Upper Moon in a battle to the death! I’m really hyped to see this scene animated! (Manga Chapter 174)

As we were saying, when the Demon Slayers almost kill Kokushibo, he suddenly transformed into a MONSTER, and the dark mark he bore began to spread all over his body. (Manga Chapter 176)

We all know what that mark means, right? And it’s not just Kokushibo who has it, but some other characters in the Kimetsu no Yaiba series.

According to a theory, those dark marks on Kokushibo resemble a symptom of the Black Death, aka the Bubonic Plague.

The bubonic plague is spread by fleas that hang out on rats, and if you catch it, you’re likely to experience symptoms like fever, chills, and weakness.

In theory, those black marks I mentioned might represent the painful black buboes that appear all over the body. (Manga Chapter 176)

The theory also suggests that Kokushibo’s name is missing only one letter from the Japanese word “Kokushibyō,” which means Black Death.

Although it’s just a theory, it’s interesting to note that the Black Death is quite a fitting comparison for the most badass Upper Moon. Both Kokushibo and the plague are capable of slaying millions of people. (Manga Chapter 171)

The Demon Slayers successfully defeated Kokushibo. However, their victory was tragic as Genya and Tokito died in that fight. (Manga Chapter 179)

Oh, by the way, we have a blog about Kokushibo’s brother: Who Is Yoriichi, Is He A Demon And What Are His Powers?

Demon Lord: Muzan

Now, the remaining Demon Slayers are entering the final boss fight… the ultimate battle to defeat the Demon Lord Muzan!

If the Upper Moons are really based on diseases, then Muzan might just be based on the worst of them all – cancer.

He’s like a cancer cell that just keeps spreading and growing, which is probably why it’s so difficult to kill him. 

In Chapter 187, we saw Muzan’s ability to split himself into a thousand pieces, just like the worst technique of cancer cells called metastasis.

Let’s not forget that sunlight is 100 percent effective against him, just like radiation therapy used to treat cancer. (Manga Chapter 200)

Before Muzan got roasted by the sun, he was weakened by the poisons created by Shinobu and Tamayo. These poisons could represent the latest cancer treatments, which turned the battle against Muzan into a symbolic fight against cancer. (Manga Chapter 193)

Conclusion

So that’s it!  And If you’re dying for more Demon Slayer content, then I recommend reading this blog: anime like Demon Slayer. Who knows, you might even discover your next favorite anime!