Who Was Upper Moon 1 Before Kokushibo? Truth Behind the Rank

When you look at the hierarchy of the Twelve Kizuki, it feels like a corporate ladder built on blood. Demons fight, kill, and absorb each other to climb the ranks from Lower Moon Six all the way to the top.

Standing at the absolute pinnacle is Kokushibo. With his six eyes, ancient samurai armor, and terrifying “Moon Breathing” technique, he commands a level of respect (and fear) that even the chaotic Muzan Kibutsuji seems to appreciate.

But given that demons have existed for a thousand years, fans often ask: Who was Upper Moon 1 before Kokushibo? Did he steal the spot from an ancient predecessor?

The Definitive Answer: No, there was no Upper Moon 1 before Kokushibo.

Kokushibo is not just the current leader of the Upper Moons; he is the architect of the position. He was the first Demon Slayer to ever betray the Corps and become a demon, and he has held the rank of Upper Rank One continuously for nearly 480 years since the Sengoku Era.

In this deep dive, we will explore the history of the man who became a monster and why the position of “Upper Rank One” was essentially created for him.

The Origins: Michikatsu Tsugikuni

To understand why Kokushibo has no predecessor, we have to go back to the Golden Age of Demon Slayers: the Sengoku Era.

Before he was a six-eyed demon, he was a human swordsman named Michikatsu Tsugikuni. While that name might not ring a bell for anime-only watchers yet, his last name should. He is the ancestor of the Tokito family (Muichiro) and, more importantly, the older twin brother of Yoriichi Tsugikuni, the creator of Sun Breathing and the strongest swordsman to ever live.

The Motivation: Envy and The Curse

Michikatsu wasn’t a villain by nature; he was a man consumed by two things:

1. Inferiority: No matter how hard he trained, he could never surpass his younger brother, Yoriichi.
2. Fear of Death: Michikatsu awakened the Demon Slayer Mark (the same mark Tanjiro and the Hashira manifest). In the Sengoku era, it was a known fact that those who awakened the mark would die before the age of 25.

The Deal with the Devil

Terrified of dying young without ever surpassing his brother, Michikatsu was approached by Muzan Kibutsuji. Muzan offered him a way to preserve his swordsmanship forever and bypass the curse of the mark: become a demon.

Michikatsu accepted, abandoning his humanity, his family, and his honor. Upon his transformation, he took the name Kokushibo. Because he was a “Breathing Style” user before turning, something Muzan had never acquired before, he was instantly vastly superior to any other demon in existence. He didn’t need to climb the ladder; he built it.

Establishing the Twelve Kizuki

To fully grasp why there was no predecessor, we need to look at the timeline of Muzan’s organization.

When Michikatsu Tsugikuni became a demon during the Sengoku Era (approx. 480 years before the main story), the “Twelve Kizuki” as we know them likely did not exist in their current structured form. Muzan was largely operating alone or with lesser, unorganized demons.

The First Elite

Kokushibo wasn’t just another recruit; he was an anomaly.

• A “Business Partner”: Unlike other demons who are treated as disposable slaves or experiments, Muzan viewed Kokushibo almost as a business partner. He was the first human to retain his Breathing Style (Moon Breathing) after transformation.
• The Foundation: Because Kokushibo was instantly powerful enough to kill Hashira-level swordsmen, he became the benchmark. It is heavily implied that the Upper Rank system was built around his existence. He didn’t fill a vacancy; he set the standard that no other demon has ever been able to reach.

For nearly five centuries, the Upper Ranks have changed faces many times (Daki and Gyutaro are relatively new, for example), but the seat of Upper Rank One has never changed. It has been Kokushibo’s throne since the day he abandoned his humanity.

The “Blood Battle” System: How He Stayed on Top

In the world of Demon Slayer, ranks are not permanent. Muzan established a system called Blood Battles (Ketsuwaru), where a lower-ranked demon can challenge a higher-ranked demon to a duel.

• The Rules: If the challenger wins, they take the higher rank. If they lose, they are usually absorbed (eaten) by the winner.

Kokushibo’s Undefeated Record

You might wonder: In 480 years, surely someone tried to take his spot? Yes, they did. According to the Official Demon Slayer Fanbook, Kokushibo has been challenged three times for the position of Upper Rank One.

• The Challengers: Two of these challengers were defeated and immediately absorbed by Kokushibo, erasing them from history.
• The Exception (Akaza): The third challenger was Akaza (Upper Rank Three). Akaza fought Kokushibo but was defeated. However, in a rare display of mercy (and perhaps respect for a fellow warrior), Kokushibo chose to spare Akaza rather than eat him.

This record is the ultimate proof of his dominance. It’s not that other demons didn’t exist before him; it’s that no demon has ever possessed the power to dethrone him. He is the immovable object at the top of the hierarchy.

Common Misconceptions

Because Kokushibo’s history is revealed late in the manga, many fan theories have popped up over the years about who preceded him. Let’s debunk the most common ones using official canon information.

Myth 1: “Akaza used to be Upper Moon 1.”

• The Theory: Because Akaza is so focused on becoming stronger and hates Kokushibo, some fans believe he was originally the top dog who got demoted.
• The Truth: This is false. Akaza is significantly younger than Kokushibo. Kokushibo has been a demon for nearly 480 years (since the Sengoku Era). Akaza has been a demon for roughly 200+ years (from the Edo Period). Kokushibo was already Upper Rank One long before Akaza was even born as a human named Hakuji.

Myth 2: “Muzan had a different right-hand man before finding Kokushibo.”

• The Theory: Muzan must have had someone else in charge during the hundreds of years before he met Michikatsu.
• The Truth: Before meeting Michikatsu, Muzan was not running an organized military operation. He was largely a solitary creature creating random, disorganized demons to search for the Blue Spider Lily. He had no “right-hand man” because he had no one strong enough to fill that role until he corrupted a Breathing Style user. Kokushibo was the first subordinate Muzan truly respected as a powerful asset rather than just a disposable tool.

Conclusion

So, who was Upper Moon 1 before Kokushibo? Absolutely no one.

Kokushibo is a unique existence in the Demon Slayer universe. He is the first demon slayer to fall from grace, the creator of Moon Breathing, and the only demon to have maintained his rank since the inception of the Twelve Kizuki.

His story is not one of replacing a predecessor, but of setting an impossible standard that no other demon, not even the mighty Akaza or Doma, has ever been able to reach. He sits on a throne built of 500 years of jealousy, regret, and unmatched power, making him one of the most tragic and terrifying antagonists in anime history.

Frequently Asked Questions

Q: How long has Kokushibo been Upper Moon 1? 

A: Kokushibo has held the position for approximately 480 years. He was transformed during the Sengoku Era (the Golden Age of Demon Slayers) and has remained undefeated in his rank ever since.

Q: Did Akaza ever defeat Kokushibo? 

A: No. Akaza challenged Kokushibo to a “Blood Battle” to try and take his rank. However, Akaza lost. In a rare act of mercy, Kokushibo chose to spare Akaza’s life rather than absorb him, which is the usual penalty for losing.

Q: Is Kokushibo related to Tanjiro? A: No, they are not blood relatives. Kokushibo (Michikatsu Tsugikuni) is the ancestor of the Tokito family (Muichiro). However, his brother Yoriichi was a close friend of Tanjiro’s ancestor (Sumiyoshi), which is why Tanjiro knows Sun Breathing (Hinokami Kagura).