The sound of wooden swords clashing echoed throughout the training grounds, sharp, rhythmic, and intense. Two figures faced each other under the morning sun, their movements blurring with speed.
Rengoku Kyojuro, his spirit blazing like a roaring inferno, swung his practice sword with unmatched vigour. Across from him, Tomioka Giyu countered each strike with calm precision, silent, fluid, like a flowing stream.
"Magnificent, Tomioka!" Rengoku bellowed between swings, his laughter echoing like thunder. "Your swordsmanship burns brighter each time we cross blades!"
Giyu said nothing, his expression as unreadable as ever, his wooden sword parrying Rengoku's attacks with effortless grace.
The clash of Fire and Water continued, two forces, perfectly opposed, yet equally awe-inspiring.
Standing at the side, Akira watched them with wide eyes; the only thing on his mind was, "Man… Demon Slayer fans would pay to see this animated."
This fight never happened in the anime or manga, but now he is getting to see it in live action.
He had once thought that without the anime's flashy effects, such fights would seem dull. But his Mystic Eyes told him otherwise. They revealed the flow of energy, elemental streams of fire and water swirling with each breath. It wasn't as dramatic as animation, but to Akira, it was beautiful in its own right.
Still, swordsmanship itself wasn't exactly his speciality. His father had once tried to train him in the art of the blade, but Akira had never taken to it.
It was like when your parents wanted you to learn dancing, but your heart was set on piano instead.
So, he turned to the person beside him, the one who probably understood martial arts better. "What do you think, Erika?"
Erika, who had been quietly ignoring him since last night's incident.
Akira, however, had learned one important rule over time: If I keep talking, she'll eventually give in.
Sure enough, Erika sighed quietly before finally answering. "They're incredible. For ordinary humans, their movements are beyond belief. And their techniques… refined and precise."
She had decided, for now, at least for now, to forget about last night's embarrassment.
Akira nodded. "It's the breathing techniques. They're using them to surpass human limits."
"Really?" Erika asked. "They can do that just by breathing?"
"It's more than that," Akira replied. "From what I can see through my Mystic Eyes, it's more like energy manipulation. They're channelling life force throughout their bodies, enhancing their physical capabilities. Each breathing style optimises the body differently."
Erika blinked. "Explain."
Akira grinned and went into full science mode. "Flame Breathing, for example, harnesses rapid oxygen consumption to raise body temperature and metabolism, converting kinetic motion into explosive strength. Every swing becomes a burst of controlled combustion. As for Water Breathing, it regulates breathing and heart rhythm to maintain a constant flow of energy, recycling momentum to conserve stamina. Smooth and continuous, like an endless current."
Erika stared at him blankly. "…Yeah, I didn't get a single word of that. Can you explain it?"
"That was the simple version," Akira said flatly.
Erika sighed. "Of course it was."
Sitting nearby, Ubuyashiki Kagaya, the Demon Slayer Corps' leader, smiled softly as he listened. "So, Hoshino Akira-kun," he said in his calm, gentle voice. "You've now observed our Hashira and their techniques. What do you think of them?"
Akira answered with a thoughtful expression. "They're impressive. It's not as flashy or powerful as magic, but it allows normal humans to fight demons on equal ground. And the mechanism behind it is quite sophisticated."
"I see," Kagaya said with a faint smile. "Then perhaps you might show us your magic in return. Everyone here would like to learn more about it."
"Sure," Akira said with a nod. He turned to Erika, who gave a small nod back. Together, they stepped into the centre of the training yard.
"Erika, move back a bit," Akira said. Once she did, he raised his hand.
"Answer me—Eclipse."
In an instant, black armour materialised over his body. The transformation was smooth, silent, and efficient, no huge black wolf and other theatrics this time.
Gasps filled the air as the Hashira instinctively shifted into battle stances.
Selena's voice echoed in his mind. "Why didn't you summon it like before? I thought you wanted to show off".
"I do want to show off", Akira replied telepathically, "but scaring them half to death isn't a good first impression".
"My, my… Brother, you've grown up", Selena teased.
"Shut up", Akira shot back telepathically, before addressing the onlookers.
"We magicians can manifest our souls into weapons or armours called Devices. They allow us to channel our power into physical form." He raised his armoured hand. "This black armour is my Device—Eclipse. Its ability is evolution."
"Evolution?" Kagaya tilted his head slightly. "Could you elaborate?"
"Basically, I can make things better," Akira replied with a grin. "Anyone got a seed?"
Shinobu, who had been silently observing, tossed him a small seed. "Is this ok?" she said with a faint smile.
"Perfect." Akira caught it and held it between his fingers, and used his power. "Rewrite."
He tossed the seed to the ground. The moment it touched the soil, it sprouted, and within seconds, it grew into a massive tree towering above them all.
Gasps and murmurs filled the training ground. Kagaya asked calmly, "What happened?"
Kagaya's twin daughters looked up at the tree and said in perfect unison, "The seed grew into a tree instantly, Father."
"I see," Kagaya said with a calm smile. "So your power accelerates growth."
"Exactly," Akira said. "I can make living things evolve instantly… but it has a downside."
As he spoke, the tree began to wither. Its leaves crumbled to dust, and within moments, the once-towering tree had decayed completely, leaving behind only grey ash.
"That's the cost," Akira said quietly. "Rapid evolution also means rapid decline. Life that grows too fast dies just as quickly."
The Hashira watched in silence, impressed yet wary.
"But I can apply this ability in other ways, too," Akira continued. "For example, I could enhance wisteria poison, make it exponentially more lethal to demons."
At that, Shinobu's eyes sparkled with excited thoughts. "If he can truly do that, then even an Upper Moon could be defeated, then maybe, just maybe…"
Kagaya's calm voice followed. "Your power could change the tide of our war."
Akira nodded humbly. "Maybe. But my power isn't perfect yet."
Then he turned toward Erika. "Now, Erika, it's your turn."
Erika nodded and stepped forward. "Serve me, Églantine."
Rose petals swirled around her arms, vanishing to reveal two long crimson ribbons extending from her wrists.
Akira gestured toward her. "That's Erika's Device. As for what it can do… we're still figuring it out."
Kagaya looked intrigued. "Why is that?"
"Well, she only awakened it recently," Akira said.
"For now, I can increase the weight of an object," Erika said softly. She picked up a small rock and tossed it lightly forward.
The rock struck the ground and exploded into a small crater, as if a boulder had fallen instead.
The Hashira watched in stunned silence once more.
Akira smiled wryly. "Like I said, we're still working on it."
Kagaya folded his hands. "I see…" His voice was calm, but his mind was already racing. If these two truly intended to help, they could become invaluable allies in the fight against Muzan.
He spoke again, keeping his word to them. "You mentioned before that you wished to learn our Breathing Techniques, correct? Which one interests you most? We also have Thunder and Flower Breathing, though there are no current Hashira from those branches."
Akira grinned. "Oh, I already learned all of them."
Every Hashira froze. Even Kagaya blinked, momentarily surprised.
"What?!" Rengoku exclaimed, voice booming like a firestorm. "You've already learned all of them? That's amazing! Truly a burning spirit of growth!"
Even Giyu turned slightly, his usual calm expression cracking just enough to show disbelief. "That's… impossible."
Only Erika didn't look that shocked knowing him; she was just slightly exasperated.
Akira continued casually, "I've already memorised all their forms and breathing patterns just by watching. Now I need to practice them. Though eventually, I'd like to create my own style."
"You mastered them just by watching?" Kagaya asked in quiet amazement.
"Not mastered," Akira corrected. "Just memorised. To truly master them, I'll need time and training."
Kagaya smiled faintly. "I see. Then what about the young lady?"
Akira turned toward Erika with a grin. "Well, as for her…"