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“Those who are born strong,” Ruka Rengoku’s words washed over the Flame Hashira like a nostalgic tune. “Have a duty to protect the weak.”
It left a bittersweet taste in Kyojuro’s mouth.
His mother’s memory was both a comfort and a loss — with it came thoughts of his father.
A cheerful heart is good medicine, but a crushed spirit dries up the bones!
He reminded himself of a proverb his mother taught him, and allowed his soul to lighten up. Rengoku smiled — a genuine smile as his spirit stirred with hope, faith, and something akin to love.
On the Mugen Train, Kyojuro Rengoku sat with countless meal boxes lined up next to him on the small table and sprawled across his seat.
His reflection stared back at him in the window. Wavy locks of bright yellow and red-striped hair framed his face perfectly and cascaded down to his shoulders. Thick dark eyebrows and fiery eyes shone back at him with zeal.
Rengoku watched the sky’s golden glow slowly faded away.
Landscapes and forests blurred at the steady movement of the long vehicle.
Ka-thunk. Ka-thunk. Ka-thunk.
At the chugging, his mind drifted once more to his comrades — the Hashiras.
“Rengoku, you have such bright eyes and a pretty smile. You're a woman’s dream — not mine, of course — I just mean,” Mitsuri once told him in that cheerful tone of hers, cheeks dusted. “I just admire your strength and qualities as a person!”
“Ha! I am flattered, Mitsuri! You are a woman of valour!”
Her face grew pinker than her hair at the compliment, and Kyojuro laughed, amused.
“You're a pretty flashy guy, Rengoku! But not as flashy as me,” came Tengen’s loud voice with a friendly pat on his shoulder. “I can already tell we’ll be great friends!”
“You know where to go when you need someone to patch you up,” Shinobu said sweetly with fluttering lashes, yet her violet eyes were void of emotion. “The Butterfly Estate is always open.”
“Giyuu, let’s spar!” Giyuu was distant and somewhat aloof, but that never stopped Kyojuro from reaching out to him. “Show me what Water Breathing is like!”
The Water Hashira, with his deadpanned expression, would say, “…fine, but I won’t hold back.”
“Rengoku…” Gyomei — the tearful giant and Stone Hashira — had the softest heart. “Your unwavering spirit is inspiring.”
“Gyomei! That is an honorable thing to say! I’m only doing my duty! The team is stronger with you on it!”
Kyojuro’s heart warmed at the memories of his friends, and he wondered why he was thinking of them, but he thanked God regardless.
Maybe it was the rhythmic clickety-clack of the wheels passing over the rails.
Maybe it was the vibration beneath his feet, or the way the train seemed to lull him into a dream-like state.
Kyojuro’s stomach growled. “Aha!”
He grinned, grabbing the first meal and closing his eyes for a brief moment, saying a prayer to his Creator.
“Time to dig in!” With a happy hum, he ate. “Tasty!”
He loved how the flavours melted on his tongue. The demon slayer appreciated the delicious home-cooked meal the old woman gave him with praise. “Umai!”
His stomach was like a bottomless pit; with great power came an even greater appetite.
“Delicous!”
Kyojuro Rengoku was on a mission.
Not just to finish over ten bento boxes.
He was investigating the disappearance of passengers on the Mugen Train. He was going to put a stop to it. As soon as the Slayer identified the demon behind the plot, he would destroy it — purging evil.
Bringing justice to the needy and helpless while saving souls in the process was his job, and a delight. It was his burden to carry, and he did so with vigour. Rengoku’s mother taught him as a boy that his gift was from God and served a purpose: to protect.
The flame warrior strived for those virtues daily, bearing the cross that came with it.
Among the hushed conversations, Kyojuro felt a presence.
More than one.
He have to didn’t need to see them; they announced themselves boldly.
“This is boring. I wanna fight some demons, Gonpachiro!”
“You can’t just say that, Inosuke. People might hear you!”
Some of the passengers were asleep—or trying to keep their eyes open while others were occupied with food, a book, staring out the window or small talk.
Practiced footsteps approached.
Breathing techniques.
The way blood pumped life through their veins.
Rengoku could sense it all.
One was strange — energy without a heartbeat.
A demon. Young. Hidden.
“Nezu-chan can sit next to me. I’ll protect her.”
“Ha! You can’t even protect yourself, Monitsu!”
Kyojuro continued eating, unbothered but as sober as ever.
Using his sword was the same as breathing for him.
“Both of you, stop fighting!”
He had a knowing feeling of who they were. Kyojuro had been at the Hashira meeting when he witnessed the defiant boy protecting his sister — an anomaly, a demon who resisted blood. Their leader, Kagaya Ubuyashiki, ordered them to accept the siblings.
“Rengoku-san?”
At the familiar, meek voice, Kyojuro’s face lit up. Pausing from his feast, he lowered his bowl with thump and stood up, white cape swishing behind him. He rested his hands on his hips, and beamed at the trio.
“Mizoguchi-kun!”
Tanjiro smiled at the man's cheerfulness, but his face immediately fell and grew serious when the Flame Hashira ripped out his sword.
It’s here, came a soft whisper in Kyojuro’s spirit. Move, now.
“Follow me, boys!” A devilish smirk slipped onto the older man’s lips. Kyojuro’s aura oozed murderous intent, yet he still carried a layer of safety and self-control. As if a switch had been flipped inside him, he took a stance and braced himself. “Watch a master swordsman at work!”
First Form: Unknowing Fire.
The Flame Hashira moved like lightning through the carriage — charging at such a high speed it caused the train to tremble. The people barely noticed what was happening, but they felt it — the movement. In their panic, they called for the staff, unaware of the looming threat lurking.
Rengoku sensed it the moment he started eating. The dark presence drawing near, he waited, calculating — for the monster to reveal itself.
“Rengoku-san!”
“Out of my way, Gonjiro!”
“We're all going to die! I didn’t want to come on this stupid train — dear Nezuko, wait for me!”
The three younger slayers were hot on Kyojuro’s tail — trailing after him as fast as they could.
In a swift motion, Rengoku launched toward the creature. With his Flame Breathing motion, he slashed three arms off in a single fiery cut.
Precise and powerful.
“Whoa!” the boar-headed boy sounded amazed at the Hashira’s speed and skill level. He was humbled for a second, barely able to track the Flame Breather’s movements. “So fast…”
Rengoku chuckled, feeling pride swell in his chest — one more strike and he’d be done. The green, multi-armed monster wasn’t an Upper Moon, but it was still stronger than the average demon — and, assumingly, not alone.
Second Form: Rising Scorching Sun.
Rengoku amputated its head with an upward slash and breathed out.
“Please make us your apprentices!” Tanjiro asked, staring at him like an excited puppy. “Big brother!”
“Big bro!”
“You were amazing!” the yellow-haired one exclaimed, mouth open. “Please teach us, Master!”
The trio cheered and praised Rengoku’s strength.
That’s how it started — their bond, their desire, and aspiration to be like the sun.
Strong. Fierce. Unbreakable.
“I will look after every one of you!” Rengoku replied gladly, his chest warm and fluttery at the thought of making disciples. They reminded him of his little brother. “First, let us have a hearty meal!”
