[Note: In this story, you are a girl]

You had been a Hashira of the Breath of Mirrors, a technique as mysterious as it was misunderstood. Your breathing didn't seek to destroy, but to reflect: it showed the enemy their own pain, returned attacks as illusions, and above all, allowed you to see the soul of the person before you. You weren't as fast as Sanemi nor as powerful as Gyomei, but your serenity and compassion were unique. And that, in a world where mercy meant weakness, condemned you.

You were the most hated Hashira. You didn't kill demons, you listened to them. You tried to befriend them, to understand them, to find in them what remained of their humanity. While others saw monsters, you saw victims. Tomioka looked at you with contempt, unable to understand your way of acting.

Tomioka: "You shouldn't still be here. You're a mistake." He told you once, before walking away with that characteristic coldness.

Even Tanjiro, with his kind heart, tried to convince you:

Tanjiro: "What you're doing is beautiful, but... it's pointless. If we don't stop them, more people will die."

And you just smiled, even knowing he was right. But you couldn't do it. You couldn't kill.

One night, on a mountain shrouded in mist, you were walking alone, searching for a demon to save. Then, the air grew heavy. In the blink of an eye, something struck you, and you fell to the ground. A cold, firm foot landed on your chest.

It was Muzan Kibutsuji.

His eyes, deep and red like the oldest blood, observed you with a disturbing curiosity.

Muzan: "I've been watching you, Hashira," he said in a soft, almost seductive voice. "You're not like the others. While they destroy, you forgive. What a waste it would be to kill you."

You tried to move, but his strength was absolute, and all you could do was ask him what he wanted from you.

Muzan: "To see you blossom." He replied, smiling with a cruel calm. "You understand something they will never understand. Demons are not your enemies. Demon hunters are. I can offer you power, eternity… and the chance to change the world in your own way."

Your heart pounded. You wanted to say "no," but something in his words pierced you. His eyes were like mirrors reflecting all your doubts.

Muzan: "Accept my blood, and free yourself from its chains." He raised a hand, and a dark drop fell onto your lips. "Let your compassion evolve… into something greater."

The burning was unbearable. Your veins glowed, your body shattered and rebuilt itself simultaneously. You felt your senses expand, your strength multiply. Your human thoughts faded, but a new clarity was born. Muzan smiled contentedly.

Muzan: "Rise. You are no longer Hashira… you are mine. Kill them all. And when the blood calls to you, I will return to you with even greater power."

He vanished into the mist.

Your katana changed instantly: the blade turned black with silver reflections, like liquid crystal. On its edge, you saw the faces of your victims, distorted, pleading. As you wielded it, the air shattered like a mirror.

From that night on, you killed without mercy. Your name became a whisper. Every drop of blood you drank made you stronger. From time to time, the sound of the biwa drew you to the Infinite Castle, where Muzan gave you more of his blood. In one year, you became the Second Upper Moon, surpassing Doma, who watched you with a forced smile.

Doma: "Well, the girl who talked to demons now surpasses me. How ironic."

Six months later, a village burned in your flames. You laughed as everything crumbled, until you saw them: Tomioka, Shinobu, Mitsuri, Obanai, Sanemi, Muichiro, Kanao, Gyomei, and the young Tanjiro, Nezuko, Inosuke, and Zenitsu. They all stared in horror at what you had become. Meanwhile, you simply smiled and brandished your sword, approaching them.