He went in Kyลjurล's stead.
Why? Nothing more than fate weaving an unexpected path.
The Flame Hashira had originally been assigned to the mission aboard the Mugen Train. However, reports of the demon's activities had escalated so rapidly that there was no time to wait. Kamisato Ayato, who happened to be operating considerably closer to the area, received the order instead. The decision was made in mere moments, driven solely by necessity.
The Lower Moon was dispatched with terrifying ease. Its Blood Demon Art, capable of trapping countless victims in dreams, proved utterly meaningless against the Water Hashira. Within moments, the demon's head rolled across the floor, defeated so effortlessly that it scarcely deserved the title of one of the Twelve Kizuki.
But Upper Moon Three was an entirely different story. Akaza was a monster beyond comparison. The moment their eyes met, Ayato understood a simple, chilling truth. A direct confrontation would end with his death.
Rather than rushing in, he concealed that realization behind the calm expression for which he was known. He entertained Akaza's endless speeches, allowing the demon to boast about the strength of the Upper Moons, the futility of human life, and the so called gift of immortality. Every passing second mattered. Ayato wasn't listening because he was tempted. He was buying time.
The eastern horizon had already begun to pale, though only someone paying close attention would notice. Sunrise was approaching, and against an Upper Moon, the sun itself was a far greater ally than any sword. Only when he judged that enough time had passed did he draw his blade with genuine intent.
The battle that followed was nothing short of catastrophic. Water and destructive shockwaves collided relentlessly, carving enormous craters into the earth and splitting ancient trees as if they were brittle twigs. Nichirin steel flashed like streaks of lightning while Akaza's Compass Needle allowed him to predict nearly every movement. Every exchange threatened to become the final one.
To the surviving Demon Slayers, the fight was nearly impossible to follow. Both warriors moved with such overwhelming speed that they vanished into blurs, their blades and fists meeting in explosive collisions that echoed throughout the forest. Ayato suffered greatly. A devastating blow shattered one of his arms. Several strikes tore through his abdomen, staining his haori crimson. Countless cuts and bruises accumulated across his body until nearly every movement sent waves of agony through his muscles. His breathing grew heavier with every passing minute, and yet he refused to yield a single step.
He only needed to survive.
The first rays of dawn finally pierced the horizon. Their golden light spilled across the battlefield, slowly consuming the darkness. Akaza clicked his tongue in frustration before abandoning the fight altogether, sprinting toward the forest in desperate search of shade. Even someone as prideful as an Upper Moon could not challenge the sun itself.
Exhausted beyond measure, Ayato planted the tip of his Nichirin blade into the earth, using it as support to remain standing as he silently watched the demon disappear among the trees. Warm sunlight fell across his bloodstained face. For the first time since the battle had begun, a faint smile appeared on his lips.
He had done it.
The mission was complete.
Though every breath burned and his vision had begun to blur, he could already hear distant footsteps. The Kakushi would arrive soon enough. His wounds were horrific, but survivable. Relief washed over him.
Not only had he protected every life aboard the train, but somewhere beyond that battlefield, another Hashira continued to live because fate had chosen a different name for this mission.