[Osamu's Deep-Dive] Why Was Kibutsuji Muzan Born in the Heian Period? The Historical Relationship Between Onmyoji and "Oni"

Hello! This is Osamu, the manga blogger.

He is the origin of all evil in Demon Slayer: Kimetsu no Yaiba, and the ultimate nemesis: Muzan Kibutsuji.

In the story, it’s revealed that he was born as the progenitor of the "Oni" (demons) over a thousand years ago, during the "Heian period."

Doesn't that make you wonder?

Why the Heian period? Not the Warring States (Sengoku) period, nor the Edo period.

At first glance, it seems like a glamorous era where aristocrats cultivated elegant (miyabi) culture...

But as I was reading the Dictionary of Magic and the Dictionary of Oriental Deities from my bookshelf, I became convinced.

The Heian period was the darkest era in Japanese history, precisely the time when an "Oni" was destined to be born.

Today, let me share my deep-dive analysis of that historical connection!

What Lay "Behind the Scenes" of the Glamorous Capital

When you think of Heian-kyō (ancient Kyoto), you probably imagine glittering aristocratic culture.

However, there was something that the people of that time feared more than anything else.

That was "Onryō" (vengeful spirits) and "Mononoke" (evil spirits).

A prime example is Sugawara no Michizane, whose name also appears in the table of contents of the Dictionary of Magic.

People at the time genuinely believed and feared that the "grudge" of Michizane, who died a wrongful death after losing a political conflict, brought thunder and plagues upon the capital. To appease his curse, they enshrined him as a "Kami" (deity) at Kitano Tenmangu Shrine, which is also listed in Japan's 200 Select Shrines.

In other words, the Heian period was an era when an individual's "grudge" or "curse" was recognized as a "realistic threat" capable of causing even natural disasters.

The Era When "Oni" Were "Real"

When we hear "Oni" today, we think of them as beings from fairy tales.

But for the people of that time, "Oni" were an object of terror, right there with vengeful spirits.

As I wrote in a previous article, according to the Dictionary of Oriental Deities, the etymology of "Oni" comes from "On" (隠), meaning "unseen, unknowable terror" itself.

Although Heian-kyō was a city, it fell into complete darkness at night.

In that darkness, plagues, disasters, and thieves were all considered the work of "Oni."

It was also during this Heian period that legends of famous Oni, like "Shuten-dōji of Ōeyama," were born.

"Oni" weren't fairy tales; they were "real calamities" lurking in the dark of night.

When "Jujutsu" (Sorcery) Was the Ultimate Technology

So how did the people of that time counter this "darkness" of "vengeful spirits" and "Oni"?

This is where the "Onmyōji" (Masters of Yin and Yang) come in.

The Dictionary of Magic also contains descriptions of Abe no Seimei, the most prominent of the Onmyōji.

They were state-sponsored specialists who used astronomy, divination, and "sorcery" to predict and exorcise (harau) calamities approaching the capital.

Just as they used invisible beings called "Shikigami" to banish curses, in this era, "sorcery" was the one and only, and strongest, "defense technology" available to fight spirits and Oni.

Analysis: Why Was Muzan Born in the Heian Period?

Organizing these points, the answer becomes clear.

Muzan Kibutsuji was a frail "human."

He became an "Oni" due to a "failed medical treatment" by a certain doctor, but his essence is an "abnormal fear of death" and an "abnormal obsession with life."

I believe that this intense "obsession" of Muzan's acted as a "curse" within the fertile soil of the Heian period.

• An era when people's "grudges" became "vengeful spirits" that shook the capital.

• An era when the calamity of "Oni" was believed to "really" exist in the darkness.

• An era when "sorcery" was a "real power" to counter those calamities.

Could there have been any era more perfect for a "curse" known as an obsession with "life" to take the "form" of an "Oni"?

Muzan's individual "curse" resonated with the "darkness" and "fear" of the Heian-kyō, manifesting as the first and strongest "Oni" in Japan...

That's what I believe. As the origin story for a frail human becoming a "demon," there could be no more persuasive setting than the Heian period.

The depth of Demon Slayer's story truly lies in how brilliantly it incorporates these "dark" parts of Japanese history into its setting.

Man, I can't stop overthinking it!

This was Osamu.