[3rd POV]
Rengoku was not sure what was going on. He didn't even regain his coherent mind until later on.
He opened his eyes and he saw someone in need so he protected them, he saved them.
It was as simple as that. It was instinct.
But as the searing heat whispered at his skin, he regained a semblance of thought. He did not know how long he slept but now he was awake and the Butterfly Mansion was under attack.
He saw a demon in front of him and he fought like he had trained his whole life to do. He slayed demons to protect people.
"You are a demon, why are you attacking me!!!" Daiyo said as he made a road of lava from his body crashing along the mountain.
They easily went past the barriers Enmu and Rui had set up and now they were in a faraway mountain, where their destructive battle wouldn't disturb the people hiding in the Butterfly Mansion.
"It doesn't matter what I am, only where my heart lies," Rengoku said while dusting himself off of the dirt and smoke.
"And my heart still lies with the Demon Slayer Corp,"
"It doesn't matter where your heart lies, you should be obeying Lord Muzan's order! You are his slave the moment you become a demon, the only way out is to grow stronger," Daiyo said as he too got back up to his feet.
"Ah! You are right!" Rengoku hit his palm as if he just realized the situation himself. But then he shrugged, "Well, it must be the doing of my comrades. I still have my freedom despite becoming a demon,"
"This is great hahahaha," Rengoku bellowed out laughter.
Daiyo just stayed there for a while, staring in disbelief as Rengoku checked out his new appearance. He was not the brightest among the Twelve Moon Demons, he was a living weapon for Muzan to order.
And the order was to destroy the mansion but here he was, too far away to even hurt anyone. The order was to kill the humans, but a demon stood in his way.
So what shall he do? He waited for a bit for the order to come. But it never came, so he was only left to follow his own decision.
Daiyo grinned, "If you still want to side with humans after becoming a demon, then you shall die alongside them,"
"Sure, that is only natural," Rengoku said while he was feeling the two horns on his forehead.
"Come at me, I am brimming with power," Rengoku said and gestured for Daiyo to come at him.
If a Hashira could rival the Twelve Demon Moons as a human, he should be able to defeat one after becoming a demon. So Rengoku was not too worried, even though the demon seemed stronger than most.
"Blood Demon Art : Hellforged Arsenal,"
Daiyo said and then his veins glowed with red and yellow. He seemed to have lava instead of blood and the liquid fire seeped out from his hand and took the shape of different weapons.
At first, it was a sword, then a hammer before it finally settled into a giant axe. The demon nodded in satisfaction before he blurred towards Rengoku.
"Interesting," the Flame Hashira-turned-demon said as he watched the demon approach him. He was a blur to the human eye but he moved slowly from his demonic perspective.
There was something inside him, the power that begged to be released. He knew like it was second nature what his Demon Art was, and it was telling him that it could do what Daiyo just did.
His heart beat with power. Rengoku felt heat coursing through his veins, fire was being pumped by his heart.
"Set your heart ablaze," he mouthed with a smile but this time it was not just a metaphor. It was literal.
His heart was set ablaze.
He gripped his hand as if holding an invisible sword. But then a flaming sword materialized from his hand, one that felt just like how his nichirin blade used to feel in his hand.
Rengoku moved, faster than he intended actually. The speed that would take proper breathing form to attain, he was able to achieve with a single step.
Rengoku was all smiles, there was not even a hint of conflict in his heart from the situation. He was a demon now, at least he should be a little affected right?
No. Rengoku's heart was sure.
"Let's see!!" he roared and then tested the limit of his demon physique.
Daiyo had a head start but in the end, they met in the middle. Rengoku swung his sword up, meeting the axe that swung down at him with such force that it could cleave through the mountain.
Fire meets fire.
Heat swallowed heat.
*BOOOOOOOOOOOOM!!!!!*
"HAHAHAHAHAHA!! Yes, this is it!! I've been waiting for this!!" Daiyo's demonic laugh filled the boiling air, ridding oxygen from the vicinity but neither needed to breathe.
"What is your name?" Daiyo asked and Rengoku was more than ready to answer.
"Rengoku Kyojiro,"
"Let's fight to our heart's content Rengoku!!" Daiyo said and that was when their clash ended and they turned into lines of yellow and orange as they started exchanging blows with each other.
The ground beneath them would turn into liquid lava everywhere they clashed. A forest fire started almost immediately but neither was affected. They danced with the flames.
It was not long until the world around them no longer resembled what could be considered normal. It looked like they were fighting on the grounds of hell.
The air warped from the heat of their battle and colours seemed to be melting off of reality. Trees ignited in waves, and stone liquefied from the force of their collisions.
Rengoku blocked another swing of Daiyo's attack, this time his weapon shifted from an axe to a warhammer. The collision created a thunderous boom that echoed through the mountain and was visible from the Butterfly Mansion.
Daiyo jumped back to create distance, his warhammer changed into a spear.
"Blood Demon Art : Lava Fangs!"
The molten projectiles drove through the air, aiming right at Rengoku who had no intention of moving. Instead, he swiped his sword made of flame and cut the spear with ease.
Daiyo launched three more spears at him.
Rengoku charged forward while cutting the spears that came at him like bullets. He carved a path through the attacks and came upon Daiyo once more.
The two demons met with a storm of sparks and fire. Daiyo conjured lava and shaped it into a whip of molten chains before he lashed out an attack.
Rengoku simply stepped into the assault.
The difference in their technique and mastery was clear. A human who had to train to get stronger easily eclipsed the demon who was given power and did not have to attain it.
The chains coiled around Rengoku's arms but he didn't flinch. Instead, he pulled Daiyo toward him with a fierce tug, gritting through the fire with a wild grin on his face. His sword just roared brighter with flames.
"Blood Demon Art : Eruption Surge!"
Daiyo slammed his foot into the scorched earth and the land cracked in all directions before molten geysers erupted from the cracks.
The lava rained down like arrows, burning through trees and melting what was left of the terrain. Sadly it did nothing to hurt Rengoku.
Flames no longer hurt him.
Rengoku dashed and spun through the downpour like a streak of light. They both clashed with brilliant lights.
"You're matching me blow for blow! A demon like you should join us! We could fight like this forever!!" Daiyo said in euphoria as heat washed over them.
"I don't fight for fun, I only fight to protect," Rengoku said, his eyes narrowed, "You invited the wrong guy, you should go for Sanemi instead,"
Their clash ended, and both demons sent each other away as their attack cancelled each other. Daiyo took the opening.
"Blood Demon Art : Smelter's Maw!"
Daiyo inhaled deeply, then unleashed a roaring torrent of white-hot flame from his mouth.
It swept over the battlefield like a pyroclastic surge, incinerating everything in its path. Even the ash disintegrated in the face of the pure, condensed inferno.
Rengoku didn't run. He dashed straight into it.
The flames swallowed him whole.
But within that blinding pillar of energy, he pushed forward. His body was a blade itself as it separated the pillar of heat. But that was not the end, halfway through, the flames began wrapping around him instead. Empowering him instead of burning him as it should.
The fire obeyed him.
Daiyo's smirk faltered for the first time.
Rengoku didn't stop. He swung his sword again and the pillar of energy aided his attack. A wide arc of flame slammed into Daiyo's chest.
Daiyo suffered a wound on his chest and he bled out pure lava from the cut.
The fight took a small pause after that. Daiyo touched his wound in disbelief while Rengoku just stared.
That last display of power showed who had the superior Blood Demon Art. Rengoku was able to control Daiyo's falmes.
Daiyo's Blood Demon Art was 'Furnance.'
Rengoku's Blood Demon Art was 'King of Flames'.
...
...
"I think I understand it now," Rengoku commented, breaking the silence. "It felt weird at first, my body felt foreign but now I've gotten used to it,"
"I should be able to do it,"
Daiyo held his breath, 'Able to do what?' he asked in his mind.
And then Rengoku finally got into a stance, a proper one.
A thick silence.
..
"Flame Breathing,"
Then massive flames erupted from Rengoku. You wouldn't know heat had sound until you saw him in this state. The flames seemed to hum like some kind of ancient monster.
Indeed...
Daiyo never stood a chance. Not by a long shot.
A great fight for him was a warm-up for Rengoku.
Daiyo fell to his knees, and he despaired. He didn't think he would ever be able to surpass Rengoku. Even Akaza did not make him feel this hopeless.
"Esoteric Art,"
That was the end for Daiyo. How could a demon regenerate when he was reduced to ash completely?
And Daiyo turned to ash, along with the mountain.
"Rengoku!!"
..
..
*BOOOOOOOOOOOOOOOOOOOOOOM!!!!*
[IMAGE]
-------------------------------------------------------------------------------------------------------------------
Author : 500 stones for extra chapter. Lets vote.