The cold wind howled across the desolate landscape, the eerie silence only broken by the rhythmic crackling of flames from Rengoku's sword. He stood firm, his fiery gaze locked on the demon before him. Doma, the Upper Moon Two, stood with an emotionless smile on his face, his frosty aura swirling around him.
Rengoku: "I won't let you harm anyone else, Doma! Prepare yourself!"
Doma chuckled, the icy mist around him shimmering as he raised his fan, his voice cold and mocking.
Doma: "You think you can defeat me, Flame Hashira? How quaint. Let's see how your flames fare against my ice."
With a sudden movement, Doma's hands blurred, and a massive Frost Lotus Bloom (Kōri no Renge) erupted from the ground beneath Rengoku's feet. The ice flower expanded rapidly, its petals curling inward, trapping Rengoku in a freezing cage of sharp, crystalline frost. The air around him became unbearably cold, his breath crystallizing in the air.
Rengoku's expression remained determined. He gripped his katana and unleashed Flame Breathing – First Form: Sun Fire. His blade shot forward with explosive speed, slicing through the icy petals. The flames burst forth, shattering the ice with a roar, but the frost still clung to his body, freezing his limbs as he struggled to move.
Rengoku: "Your ice may slow me, but it won't stop me!"
With a powerful thrust, Rengoku unleashed Flame Breathing – Second Form: Rising Scorching Sun. A flaming arc slashed upwards, cutting through the frost and sending it flying into the air. Doma's icy form flickered as he teleported to the side, grinning.
Doma: "Impressive, but not enough."
He swung his fan wide, releasing a blast of ice and sharp shards towards Rengoku. Glacial Tessen (Kōri Tessen). The shards sliced through the air with terrifying precision. Rengoku reacted instantly, raising his blade in defense, using Flame Breathing – Fourth Form: Blooming Flame Undulation to block the incoming projectiles, the circular motion of his sword creating a shield of flame to burn away the ice.
The battlefield was now a violent clash of fire and ice, steam rising from the collision of both elements. Doma's eyes narrowed as he moved with blinding speed, sending a storm of Crystal Frost Rain (Kōri no Shigure) from above. The icy needles rained down like a blizzard, each one capable of puncturing steel. Rengoku dodged and weaved through the storm, his flame-imbued speed allowing him to avoid the deadly crystals, but several struck him, leaving cuts across his body.
Rengoku: "You can't win, Doma!"
In a blur, Rengoku leaped into the air, unleashing Flame Breathing – Fifth Form: Flame Tiger. The slashes from his blade turned into roaring flames, taking the form of a massive tiger made of fire. The fiery beast leaped towards Doma, roaring with fury.
Doma's smirk widened as he called forth his next move. Frostbound Appendage (Kōri no Shū). Ice tendrils shot from the ground, wrapping around the flaming tiger, freezing it in place as it struggled against the frozen restraints. The ice quickly spread up Rengoku's sword, trying to encase him entirely.
Doma: "This is the end, Flame Hashira. Your fire will be extinguished."
But Rengoku refused to falter. With a cry of determination, he shattered the ice with a burst of flame from his sword, his spirit burning brighter than ever.
Rengoku: "You're wrong! I won't let you win!"
Using Flame Breathing – Sixth Form: Rengoku, Rengoku surged forward, his entire body enveloped in a blazing inferno. The ground cracked beneath him as he charged at Doma with devastating speed. The flames took the form of a roaring dragon, enveloping Rengoku as he dashed toward the demon with the force of a natural disaster.
Doma's expression shifted, finally showing a hint of concern. He quickly raised his hand, summoning Frozen Heaven's Judgment (Kōri no Tenka). The air around him plunged into a deadly cold, freezing the very earth beneath them. A thick layer of ice spread in all directions, and the ground beneath Rengoku's feet began to crack and freeze, slowing his charge.
Rengoku's flame dragon collided with the ice, but the cold was too much. The icy blast swept through the area, freezing Rengoku's legs in place, slowing him down just enough for Doma to counter.
Doma: "This is the end. Your flames can't withstand my ice."
But Rengoku didn't give up. With his sword still burning bright, he broke free from the ice, his body surrounded by flickering embers.
Rengoku: "I'm not done yet!"
He leaped into the air, ready to launch one final strike when suddenly, the first light of dawn broke over the horizon, casting a warm golden light across the battlefield. The sun began to rise, and Doma's body visibly stiffened. His expression twisted into one of frustration as he felt his Blood Demon art weaken under the sun's rays.
Doma: "No… I cannot afford to fight in the daylight. This isn't over, Flame Hashira!"
With a final sneer, Doma summoned one last Glacier Ascendant (Kōri no Tate), encasing the area around him in a towering fortress of ice. Before Rengoku could strike, Doma disappeared into the ice, retreating into the frozen expanse.
Rengoku stood in the cold light of dawn, his breathing heavy but steady. The battlefield was silent, save for the crackling of his flames. The sun had risen, and Doma had fled.
Rengoku: "Doma… you won't escape forever. I'll stop you next time."
The heat of Rengoku's flames faded into the cold morning air as the fight ended in a stalemate, both combatants battered but not broken. Doma had escaped, but the war was far from over.
Rengoku didn't have the chance to use his final trump card, the "Mark of the Slayer," as Doma fled before he could activate it.
Standing amidst the remnants of their battle, Rengoku felt a surge of excitement and pride. He had survived an encounter with an Upper Moon without relying on the Mark. With a deep breath, he silently thanked Little Lord for the rigorous training and the potions that had enhanced his abilities. His mind raced with gratitude for the improvements that had helped him hold his ground against such a formidable opponent.