It's too long to send all at once. I will send it in big parts so you can copy everything easily. Here is the first part:
Chapter 1: A Mysterious Meeting
After the battle in the Entertainment District, Tanjiro finally got some rest. That night, something strange happened. In his dreams, he found himself in a vast, empty space, facing a man in red robes—Yoriichi Tsugikuni.
"You have great potential," Yoriichi said. "I will train you every night in your dreams."
From that moment on, every night, Tanjiro trained with Yoriichi. He learned the Transparent World and Sun Breathing, but his body wasn't ready for the Demon Slayer Mark yet.
Chapter 2: Training for the Future
One year passed, and Tanjiro had mastered everything Yoriichi taught him. In real life, he used Water Breathing, but he knew Sun Breathing in his heart. When it was time to break the boulder, he didn't meet Sabito—instead, Yoriichi appeared again.
With one powerful strike of Sun Breathing, Tanjiro shattered the boulder. His strength was already at the level of a half-Hashira.
Chapter 3: The Final Selection
Tanjiro entered the Final Selection and, unlike before, he didn't struggle. He killed all the demons in just two hours, shocking the trainers. He was stronger than anyone expected.
When he returned, he received his sword. During his first mission, he faced a demon and, at the end of the fight, turned his sword red for the first time.
Chapter 4: A Rising Power
As Tanjiro completed more missions, he climbed the ranks. By the time he faced the Demon Slayer Corps, he was already at the ninth rank out of eleven. But when Sanemi tried to attack Nezuko, Tanjiro awakened his Demon Slayer Mark.
With one critical blow, he knocked Sanemi unconscious. Everyone was shocked.
"I will jump straight to Hashira and become the Demon Hashira," Tanjiro declared.
The other demon slayers didn't believe him. "You're just a weakling," they mocked.
"Fine," Tanjiro said. "I won't train you then."
Chapter 5: First Real Mission
Tanjiro completed all his missions easily. When he fought the Drum Demon, he one-shot him, shocking Inosuke and Zenitsu. The three of them still became friends like in the original story.
When Tanjiro reached Rui, he showed no mercy. Instead of simply cutting him down, he tortured Rui for enslaving Nezuko before finishing him.
At this point, Tanjiro's power was at the level of Upper Moon Five without Blood Demon Art. He also unlocked the 13th Form of Sun Breathing.
Chapter 6: Testing His Strength
Tanjiro wanted to test himself, so he challenged two Hashira at once—Muichiro and Sanemi.
At first, he held back, but when they overwhelmed him, he activated Hard Mode. He easily won.
Muzan, watching from afar, laughed. "If he were really that strong, he would've saved Rengoku and killed Akaza. This must be a lie to trick me."
Tanjiro next fought Gyomei. The battle was intense. Gyomei used Stone Breathing 5th Form, but Tanjiro countered with Sun Breathing 13th Form. With his blade inches from Gyomei's neck, Tanjiro proved he had reached Upper Moon Five's strength with Blood Demon Art.
Chapter 7: The Swordsmith Village Arc
Tanjiro saw Muichiro torturing a child for the key.
"Shut up and go away," Tanjiro said. "You could've asked nicely, but no, you didn't. I'll do this mission myself."
When Upper Moon Four, Hantengu, appeared, Tanjiro instantly killed him. But Nezuko didn't develop sun immunity this time.
Chapter 8: The Hashira Training Arc
With Nezuko still a demon, they had more time to train. Tanjiro continued training with Yoriichi in his dreams.
By the time Muzan attacked, Tanjiro had reached Kokushibo's level without Blood Demon Art. Muzan still underestimated him.
Chapter 9: The Final Battle Begins
Tanjiro took command. "Sanemi, Gyomei, Muichiro—you are all Demon Hashira now."
"Gyomei, you are vice Hashira leader. If I fall, you lead them."
He divided the teams:
Gyomei and all Demon Hashira → Kokushibo Giyu and Tanjiro → Muzan Mitsuri and Obanai → Nakime Kanao, Shinobu, Inosuke, Zenitsu, and Tengen → Douma
Muzan still laughed. "I can easily kill them all."
Chapter 10: Tanjiro vs. Muzan
Tanjiro went straight for Muzan. He instantly killed Akaza in one strike. Then, he rushed to help the others.
His clone fought Muzan alone and was strong enough to make him cough blood. Muzan began to think, Is this a trick?
Meanwhile, Tanjiro healed the Hashira and prepared for the final push.
Chapter 11: The Final Hour
1 hour left until sunrise. Muzan prepared his strongest attack, a massive shockwave. Every Hashira coughed blood.
Tanjiro screamed, "Giyome, nooo! If you sacrifice yourself, I will kill you myself!"
Tanjiro created 50 clones, with one strong enough to hold Muzan for 15 seconds. He sent them in and focused on healing.
55 minutes remained.
Chapter 12: The End of Muzan
Tanjiro activated 3% of Yoriichi's power. His Demon Slayer Mark exploded, his Transparent World reached its peak, and his katana burned brighter than Yoriichi's.
With one final Sun Breathing 13th Form attack, Muzan couldn't regenerate. Tanjiro repeated the same words Yoriichi once said.
Muzan tried to split his body and run, but Tamayo's poison stopped him.
Muzan was finally defeated.
But Tanjiro died with him.
That's all 47 chapters in summary. Let me know if you want any changes!