Chapter Text
When Tsugikuni Yoriichi was born with his twin brother, they were considered a bad omen. While his older brother was the loved child who got all he could ever ask for, Yoriichi was the exact opposite.
Tsugikuni Michikatsu had the best meals, he had big room and all the toys you could think of. He had his personal teachers and many books and friends to keep him company.
Tsugikuni Yoriichi was nothing like his elder brother. He was the hated child. He couldn't go out of their house. His food was the same as servant's. His room was even smaller that servant's, with only one old futon.
But Yoriichi never complained.
He was glad he was allowed to live.
He was glad their father let him stay in their house.
He was glad his father listened to their mother's pleas and didn't kill him right after his birth.
While he never got to know his brother well (because their father forbid them to talk to each other), Yoriichi knew his brother was a very kind man. If he wasn't, why would he give him the flute? Flute he made with his own two hands. That day, for the first time in his life, Yoriichi smiled and talked to his brother. It seemed to surprise his brother. But Yoriichi didn't understand why? Apparently, they thought he was deaf. He wasn't. He just didn't see it as a necessity to talk to anyone. He just wanted to be with his brother and their mother and see them both happy and smiling. But he knew that drem couldn't become true. His mother had little over a month left to live, after all...
Yoriichi saw his brother practicing sword with his teacher.
"Brother your dream is to become the strongest samurai in the land, right? I want to be like you as well. I will be the second strongest samurai in the land."
There was a pause. This was the second time Michikatsu had heard his brother talk. And than... Another miracle happened. For the second time he saw his weak younger brother smile. A honest smile which shone brighter than the sun itself.
"I want to be the second strongest, so that I can be with brother forever and I can keep supporting you for the rest of my life."
The teacher decided to amuse Yoriichi for a bit and gave him a practicing sword. He showed him how to hold it properly, but that was all. He told him to attack. No one expected Yoriichi to land even one hit. But in seconds too fast for them to see, the instructor was lying down on his back, three dark bruises already forming on the spots Yoriichi just hit, with Yoriichi's practicing sword at his neck. In that moment, Michikatsu couldn't help but feel extremely jealous, for his younger brother, who is only a weak beta, somehow took to the sword like fish to water, while he, a strong alpha spent three years of training.
Three years of training, and Michikatsu is still not good enough to get even one hit at his teacher... While his younger brother, who is always clinging to their mother's side and running to her the moment he sees her, was able to hit three times in less than one second...
Just how is this possible?
And now Yoriichi said the stupidest thing Michikatsu had ever heard.
"I'm sorry brother. It seems like I won't be able to be the second strongest and support you."
"What? What are you talking about. That was... That was amazing... Why wouldn't you be able to be the second strongest?"
"I hate how it feels to hit people."
Somehow, this information spread like wildfire. And suddenly Yoriichi's and Michikatsu's positions were exchanged.
The one who was now supposed to lead their family was no longer alpha Michikatsu.
No.
Now it was supposed to be beta Yoriichi.
The genius beta son of the Tsugikuni family head.
But something unexpected happened.
On the night before official announcement about Yoriichi's inheritance, he appeared at the tiny door to his old room - now Michikatsu's - and said:
"Brother. Mother passed away. I will also leave early in the morning. I will head to the temple, where I was supposed to always be. The position of the head of this family belongs to you. I don't want to take it away from you."
The next day, Yoriichi was nowhere to be found and their mother's body had been taken away. Father send a search party to the temple to take Yoriichi back. But according to the people at the temple, Yoriichi never came to them in the first place.
That night, Michikatsu found his mother's old diary. Apparently, Yoriichi figured out about mother's illness. He wasn't clinging to her... He was supporting her left side as she walked, because she grew weaker and weaker everyday. He also predicted, that his father will want to make him the head of the family, that's why he decided to leave before that could happen. Where he headed to, even their mother didn't know...
After that, 10 years had passed and Michikatsu already had his own family.
He thought he would never seen his brother again.
No one would have imagined it will be exactly this same, missing brother that would save him from his death by the hands of a demon.
In the light illuminated by the moon, Yoriichi looked like the Sun God their mother was always praying to. That night, Michikatsu knew... That his brother became even stronger than before.
And somewhere deep down he also knew he would never be able to surpass him.
But his pride did not and never will let him accept that.
The jealousy he felt when he found out the truth from his mother's diary was back.
That's why he abandoned his new family.
That's why he abandoned his wife and two sons.
That's why, he became demon Slayer together with his brother.
So that he could surpass him.
And just when he thought he was finally going to be just as strong as Yoriichi, the marked ones started dying one after another... Before they reached the age of twenty-five.
And Michikatsu was ready to just give up on his dream of surpassing his brother.
And than he met Kibutsuji Muzan.
And his new life as a demon began.
With demon power, he was sure he could surpass Yoriichi.
He was sure.
But in the end, he did not.
On that night, four hundred years ago, there was a blood moon out. And Kokushibo saw something unbelievable. His 'younger brother', now looking decrepit and old was right there, standing in front of him.
The last time they saw each other was sixty years ago. So Yoriichi who stayed a human should have been over the age of eighty. Kokushibo couldn't believe his eyes.
"Impossible... How are you alive?... Everyone should be dead. Dead before the age of twenty-five. How are you... How are you the only one alive?"
"This is heart-wrenching, my brother."
The aged and hideous being that Kokushibo once called his brother was pitying him.
And yet... Kokushibo felt no anger. Even though Yoriichi had been an utter eyesore to him sixty years ago.
The voice that called him brother was extremely hoarse. His younger brother who had never showed the tiniest shred of emotions, was crying salty tears, and for the first time in his life, Kokushibo felt something swelling inside him.
Kokushibo was confused and bewildered beyond belief.
He had to kill that remnant of flesh from his human days...
That physically brittle and old man who was far beyond his prime.
As long as he was a Demon Slayer, Kokushibo had no choice but to kill him if he pointed his sword at him.
But these strange feelings were blown away in the next moment.
Kokushibo felt it... The weight of the air increased from the pressure, and it was hard to move. As if there was a boulder on each of Kokushibo's shoulders.
Yoriichi's stance was impeccable.
"Here I come."
Kokushibo wanted to draw his sword, he found his hand flying in the air. He didn't even notice when Yoriichi moved. And he barely avoided having his head sliced off.
"My deepest sympathies, my brother."
Hatred and jealousy, irritation and defeat twisted through every organ in Kokushibo's body.
'Why did Yoriichi always have to be the special one?!'
But the next attack never came.
These were the last words Yoriichi said in his life, as tears fell from his eyes. Yoriichi died in front of him not by his hand, but a natural death from old age, as he stood on his feet.
Michikatsu knew, had Yoriichi taken one more breath, he would have died that night.
Yoriichi was special.
Yoriichi was able to live even with the mark.
Yoriichi almost killed the man Michikatsu - now Kokushibo - called master. The one man a whole organizations is trying so desperately to kill, but no no avail.
Yoriichi died on his two feet, with sword in his hands, looking once again, like the Sun God himself.
And the only thing left after him was that stupid flute.
Flute, which Michikatsu - now Kokushibo - for some reason couldn't leave behind, and always kept it close to his heart.
The flute was always with him.
It reminded him of his younger brother Yoriichi.
It was his last memento on his life as a human.
He could never atone for his sins.
For he did not regret becoming demon.
It gave him the power he always wanted.
He regretted he couldn't be the one to kill Yoriichi. Because now he can never surpass him.
And than... A boy named Kamado Tanjiro shoved up in from of him.