The Story of Upper Moon 1 Kokushipo, Why Did He Become A Demon?

In the Demon Slayer Manga, Kokushipo is the most powerful demon among the Twelve Kizuki. Kokushibo’s fighting prowess was second only behind the Demon King Muzan. He was the first demon that utilized Breathing Styles. And he held the position of Upper Moon 1 over the past centuries. There is a significant difference in strength between Kokushibo and other Upper Moon demons.

But when you take everything into consideration, Michikatsu is an honorable and powerful swordsman. However, as a swordsman, what he pursues is eternal power, it doesn’t matter if he was a demon or not, as long as he turns his body and combat skills into eternity, he is still a swordsman.

And what Yoriichi pursues, as a swordsman, is to fight to the end with human flesh and blood.

Twin Born, Everything Seems to Be Destined

Kokushipo was born almost 5 centuries ago and his birth name was Michikatsu Tsugikuni, Michikatsu had a younger twin brother and the twins name was Yoriichi Tsugikuni, the same Yoriichi who would go on to become the strongest and the original demon slayer and the original breath of the sun user.

Michikatsu and Yoriichi came from a prominent Samurai family and at this time, during the Sengoku period, having twins was actually considered a bad thing since they are born at practically the same time, which could result in fights over who will inherit the father’s land and titles.

To make things worse, this was a very superstitious time, and Yoriichi was born with a strange birthmark on his face. So the father decides that the best thing to do would be to simply eliminate Yoriichi and keep Michikatsu.

Thankfully, Michikatsu’s mother refused to let this happen and she became so angry and aggressive that her husband agreed to spare Yoriichi’s life.

Instead of eliminating the younger twin, the family would raise him until he reached the age of 10 and then they would send him away to a temple where he would become a monk.

Due to the fact that monks usually have to renounce all of their worldly possessions, Yoriichi would no longer have any claim to the family’s land and titles. And so Michikatsu would be able to succeed his father as the head of the family without any problems. 

Children Growing, The Tables Turned

So the two twins were raised completely differently. Michikatsu was groomed to be the head of the family and he had better living quarters, better clothes, better food, better education and so on.

While Michikatsu was busy preparing himself to one day succeed his father, Yoriichi became extremely attached to their mother and he would always cling to her left side.

Michikatsu felt bad for his little brother. So he would often sneak into his brother’s room in order to play with him. Michikatsu wasn’t able to give Yoriichi any of his possessions because their father would notice and get angry. So Michikatsu gave his brother a small wooden flute that he had made himself.

Now Yoriichi wasn’t exactly a normal child and this further contributed to his black sheep status. For instance, he never smiled, not even as a baby and he didn’t even speak until the age of seven. Everyone basically concluded that Yoriichi must be deaf and so would never be able to speak properly. But as it turns out Yoriichi wasn’t deaf.

As his brother learned one day when he was practicing with his sword in the garden, Yoriichi was just standing silently behind Michikatsu and watching him, but then suddenly he actually said something, he said: “my brother, is your dream to become the strongest Samurai in the nation?” Michikatsu was so surprised to hear his brother actually speaking that he gasped and dropped his wooden sword. Yoriichi then said that he also wanted to become a Samurai.

But Michikatsu knew that when he turned 10, Yoriichi would be sent to a temple, he was destined to become a monk, not a Samurai. Then Michikatsu saw his brother smile for the very first time, and to him this was an odd and unsettling sight.

After this, Yoriichi started hanging around his brother and the family’s swordsmanship instructor during their swordsmanship training and he expressed a desire to learn the way of the sword.

The instructor didn’t see any harm in letting Yoriichi practice with them. So he gave him a wooden practice sword. But after only a few words of basic instruction, the instructor asked Yoriichi to try and hit him.

Michikatsu wasn’t expecting anything much because he himself had never succeeded in landing a single hit on their instructor, no matter how hard he tried, but then, the seven-year-old Yorrichi managed to land four strong blows on their instructor in the blink of an eye. And these four strikes were so strong that they knocked the instructor out.

Yoriichi’s blow didn’t break any bones or cause any permanent damage, but they left massive lumps on the instructor’s body in the places where the wood had hit.

Following this incident, Yoriichi stopped saying that he wanted to become a Samurai, he hated the feeling of hitting someone and he didn’t want anything to do with that type of life.

But Michikatsu was amazed and he wanted to know the secret behind Yoriichi’s strength, so he kept pushing him to explain how he became so strong. That is when we learned that even as a kid, Yoriichi could see into the transparent world. So he could anticipate his opponent’s movements based on the position of their bones, the contractions of their muscle, the flow of their blood and so on.

Yoriichi was also born with exceptional strength and speed. That is when Michikatsu came to a startling conclusion, all this time he had felt sorry for his younger brother, but the truth was that Yoriichi was much more talented than he was. Now Michikatsu worked hard and he had talent, so he certainly made progress and he became stronger. Unfortunately for him, his progress was nothing compared to Yoriichi who was just an unrivaled genius.

Even though Yoriichi wasn’t interested in the Samurai life anymore, after the instructor told their father about Yoriichi’s unsurpassed talent, the father abruptly changed his mind about his successor, he now wanted the incredibly strong and talented Yoriichi to take over as the head of family instead of Michikatsu.

Michikatsu was now forced to sleep in that small isolated room where Yoriichi had been sleeping all this time. To make things even worse, Michikatsu was now going to be sent to a temple when he turned 10 instead of Yoriichi, which meant that Michikatsu ‘s lifelong dream of becoming a Samurai was now impossible.

But then one night, Yoriichi came to tell Michikatsu that their mother had died. Michikatsu was shaken by this revelation because he didn’t think that there was anything wrong with their mother. But Yoriichi just told them to ask her servant about the details because he will now be departing for the temple.

Michikatsu was confused since Yoriichi was no longer being forced to be a monk. But Yoriichi knew that his father was now planning to send Michikatsu instead of him and so he decided to go before their father could do that, Yoriichi said that he will bring that wooden flute that Michikatsu had made for him so that he could feel like his brother was always with him and then he left.

Michikatsu thought that flute was poorly made and a piece of junk, and he was surprised to see Yoriichi acting like it was some sort of treasure.

After Yoriichi left, Michikatsu read his mother’s journal and he realized that his mother had been suffering from an illness for years that Yoriichi had sensed it. This illness was affecting the left side of their mother’s body, so when Yoriichi was clinging to that side, he wasn’t really clinging. He was actually helping to support her because her body had been weakened by illness.

That is the point at which Michikatsu fully understood that Yorrichi was far more observant and talented and compassionate than him. Yoriichi just seemed to be good at everything and because of this, Michikatsu began to burn with jealousy, he even began to feel hatred for his own brother because he just couldn’t accept that no matter how hard he tried, Yoriichi would always be better than him at everything.

This is ironic, because back when Yoriichi was being treated as the black sheep of the family, Michikatsu felt sorry for him and he tried to help him. But it seems that in his own mind, Michikatsu had also accepted the idea that he was superior to Yoriichi. So when the tables turned then Yoriichi showed himself to be superior and then everyone started treating him as superior, Michikatsu’s ego couldn’t handle it and he began to wish that his brother had never been born.

Luckily, Michikatsu’s jealousy subsided after Yoriichi disappeared from his life. Yorrichi had vanished and no one could locate him. Michikatsu’s father went to the temple but the monk there said Yoriichi hadn’t ever visited here. So Michikatsu’s father had no choice but to make Michikatsu his heir once again.

Chasing The Dream, Being Stronger

Ten years passed, Michikatsu settled down and started a family. His days were quiet and boring. He enjoyed a comfortable and uneventful life.

However, that comfort was broken when a demon attacked Michikatsu and his men in the forest. The demon killed Michikatsu’s men and he was about to kill him too when adult Yoriichi showed up and took the demon down in an instant.

The moment that Michikatsu met Yoriichi again. He knew that Yoriichi had mastered the sword and that he was an incredible warrior, Michikatsu’s serenity was destroyed once again. And he began to burn with jealousy.

Yoriichi was unbelievably strong and he had an impeccable character. Michikatsu decided that he would do anything to become as strong and skilled as his brother. Michikatsu went so far as to abandon his family and dedicate his whole life to following in Yoriichi’s footsteps and becoming a demon slayer.

Michikatsu trained under Yoriichi and he learned breathing techniques directly from his brother, but none of the other demon slayers, Michikatsu included, were able to attain the full extent of Yoriichi’s power. They could never reproduce the breathing technique that he used, the breath of the sun.

So Yoriichi changed the breathing techniques slightly as he taught them in order to make it possible for them to actually learn and master these techniques. That is how all the many derivatives of sun breathing emerged and one of those derivatives was Michikatsu’s own moon breathing.

Eventually, Michikatsu manifested a demon slayer mark identical to the one that his brother was born with.

Desperation, Fall into The Demon

And I mean when you take everything into consideration, Michikatsu was an incredibly powerful swordsman and demon slayer.

But despite his impressive strength which was far far above average, Michikatsu still couldn’t come even close to matching Yoriichi. No matter how hard he trained and no matter how much his life was dedicated to getting stronger. Michikatsu was simply unable to learn sun breathing and he could never rival the superhuman abilities of his brother.

And then there was another major problem, all the demon slayers who had managed to manifest the demon’s hair mark began to die off after reaching the age of 25. The demon slayer mark allowed the slayer to unlock power, but in exchange for that power, it drastically reduced the demon slayer’s lifespan.

Michikatsu realized that he was going to die without ever even coming close to achieving his dream of becoming the strongest Samirai and surpassing his brother.

And in that moment of weakness and desperation, he was approached by the crafty demon king Muzan.

Muzan told Michikatsu that if he became a demon, he could live forever and he wouldn’t have to worry about dying at the age of 25. He would also have a much stronger body and he would have all of eternity to become stronger than Yoriichi.

And so, even though he dedicated his whole life to ridding the world of demons, Michikatsu’s Jealousy got the best of him. He agreed to consume Muzan’s blood and become a demon, in exchange for eternal life and super human power, that is when Michikatsu Tsugikuni became Kokushipo. 

What is the Pride of a Swordsman

And yet, even after 60 years of being a demon, Kokushipo still couldn’t overcome Yoriichi, the two brothers faced off against each other when Yoriichi was already in his mid-80s.

Unlike the other demon slayers who manifested the demon slayer mark. Yoriichi didn’t die at the age of 25. This tells us again that Yoriichi was simply not the average demon slayer. He was always special.

Since he was a demon, Kokushipo didn’t age and he was still at peak strength even though he should have been like 85 years old. Meanwhile, Yoriichi who was not a demon really was 85 years old and he was now a frail old man.

And yet, even after six decades, Yoriichi was still stronger than Kokushipo. His technique was so exceptional that he defeated the demon kokushibo despite his advanced age. Kokushipo was down for the count and at Yoriichi’s mercy, but then Yoriichi died of old age before he could strike the finishing blow against his brother.

And so Kokushipo lost the battle but he managed to survive. This meant that for the next 400 years, Kokushipo had to live with the knowledge that even as an old man, Yoriichi was still far stronger than him.

And if all of this wasn’t bad enough, when Kokushipo cut down Yorrichi’s lifeless body. Following Yorrichi’s death, he found a small wooden flute that he had made for his brother back when they were children. Yorrichi still treasured that stupid crappy flute that his twin brother had made for him all those years ago. And that’s despite the fact that this same brother betrayed the demon slayers and became a ruthless demon.

So, not only was Yoriichi still stronger than Kokushipo even though he was a human in his 80s and Kokushipo was an immortal demon, but also Yoriichi was a man of impeccable character and boundless compassion, something that Kokushipo could never hope to be.

Kokushipowas jealousy destroyed his honor, his character and his compassion. And so no matter how many centuries Kokushipo would ultimately get to live, his long-dead brother would always remain superior to him, not only in strength, but in all those categories as well.