Chapter Text
It was a red mark in the Ubuyashiki family history.
The most brutal, tragic, and yet successful day in the history of the Demon Slayer Corps. Five years ago, to the day, was the Battle of the Infinity Castle, in which every remaining Upper Moon was defeated. It was also the battle in which they lost both the Insect and Mist Hashira, and was quickly followed by the deaths of the Love, Serpent and Stone Hashira. A day full of losses and victories.
It had seemed like the fight against the Demon King would’ve finally ended that day. The sun had been about to rise, and Kibutsuji was cornered. Despite all the losses they’d suffered, it had seemed worth it. Everything would’ve been worth it. All the suffering and violence they’d experienced the past five hundred years would’ve ended that day.
That is, if Kibutsuji hadn’t had a backup plan.
A backup backup plan, technically. They thought that the Demon King’s trick with the Castle had been the backup plan, but they hadn’t accounted for his other schemes. They would suffer the consequences of that mistake soon enough.
Just as the sun had peaked out above the horizon, with Kibutsuji impaled on the Kamado brat’s sword and desperate to escape, he released his final defense. One of his long, disgusting tentacles reached out, slashing across the mass of demon slayers left to fight him. It ripped through limbs and flesh, and the true damage would become apparent only a few seconds later.
As the attack hit, Kibutsuji pumped his blood his the victims through the tentacle, quickly infecting dozens of demon slayers at once. The results were immediate, with every slayer struck quickly dropping to their knees, screeching in agony as the blood rushed through their bodies. Even the strongest among them, despite fighting to stay standing, fell eventually.
Fangs and claws tore through the slayers’ pre-existing features, along with occasional horns and tails. Markings spread across their skin, which was rapidly paling. Snarling and wailing filled the battlefield, distracting the remaining Hashira from their attacks.
The attack had ripped the hanafuda brat and Water Hashira off of him, launching them back and into the mass of turned slayers.
The other slayers unlucky enough to be closest to the newly turned demons quickly turned to face them, blades at the ready. But the wave of new enemies was enough to knock many of the demon slayers off their feat, leaving them to suffer the brutality of their comrades attacks. For every demon decapitated, another slayer dropped to the ground. Even the hanafuda brat experienced difficulty focusing fully on the Demon King.
The chaos was enough for Kibutsuji to escape.
With his remaining anger overruled by his fear of the sun, Kibutsuji fled. He launched himself away from the battle, quickly making his way across the remains of the city and towards the nearby woods. The Water and Wind Hashira desperately followed after him, along with Kamado, the only ones who were able to keep up with the Demon King. They released attack after attack, doing anything in their power to prevent Kibutsuji from surpassing the tree line.
But to their avail, the demon managed to duck under the trees and into the shadow, just as the suns rayed started burning his skin. He didn’t stop running, and continued to race through the forest. Meanwhile, his tentacles ripped through the trees behind him, slowing down his pursuers. Even their most powerful attacks couldn’t stop him.
The distance between the demon and slayers grew steadily, until Kibutsuji disappeared from sight completely, and a few moments later from Kamado’s senses as well. Even with his enhanced sense of smell, the boy could not pick up his trail again.
Despite every instinct screaming at the three of them to keep chasing after Kibutsuji, they decided to turn back.
The aftermath of the battle was brutal. Dead slayers were scattered all over, along with the empty uniforms of the turned demons, who all disintegrated as soon as the sun rose, leaving no remains behind for them to bury.
But it wasn’t just the lower ranks who had suffered losses. Soon enough the Kakushi found the Love and Serpent Hashira, who had died in each others arms near the end of the battle. The Stone Hashira was on his last breath as well, demanding the healers to focus on others first. The damage done by the Demon Slayer Mark would be enough to finish him off soon enough.
And the damage didn’t end at deaths. There were hundreds of wounded slayers and citizens, suffering from slashes and missing limbs. Kamado himself was starting to feel dizzy from blood loss, and he desperately clutched at his missing arm. Tomioka, next to him, was mirroring his movements, and Kamado could see a steady flow of blood streaming from where the Water Hashira’s right arm used to be.
As soon as the Kakushi spotted them, they were both forced to sit down and be treated, despite them wanting to help with the cleanup. At the healers’ orders, the two remained where they were, watching as hundreds of slayers’ bodies were carried away from the site.
Despite the victories, both of them were filled with nothing but dread.
Kibutsuji was still alive.
This fight wasn’t over.
And every slayer on that battlefield knew it. They knew that the Corps would not stop fighting until Muzan Kibutsuji was dead and defeated. No matter how long it took.
Five years.
It took five years before the real battle started again. Five years before Kibutsuji revealed himself once more. Five years of preparing for a battle that could happen at any moment. Silently training new slayers, promoting new Hashira, reorganizing and planning.
For five years, not a single demon was spotted, to the point some began to question there existence as a whole.
Until now. Until the fifth anniversary, when a Kasugai Crow rushed towards the Ubuyashiki Manor, sent by a slayer stationed in Tokyo. The letter, once opened, was rushed to Kiriya Ubuyashiki immediately.
A demon had been decapitated in a Tokyo alleyway during the last new moon.
A demon had been decapitated.
A demon.
They were back.
He was back.