Shinjuro's strike severed the tail, spraying black blood. But Shima's flesh writhed, and a new tail, covered in even colder metallic scales, regenerated before it even hit the ground.
"Hiss—the Flame Hashira?!" The demon shrieked, its pupils locking onto the fiery figure. It ignored Tatsuya and lunged at Shinjuro, its claws seeking his heart while its tail swept in as a hammer.
Shinjuro let out a booming laugh. "Demon! I am your opponent!"
Flames erupted from his feet as he charged. His Nichirin Sword whirled in a ferocious defensive arc. "Flame Breathing, Fourth Form: Blooming Flame Undulation!"
The vortex of fire parried the claws and sucked the tail into its heat. Screeeech! The friction of steel on scales sparked violently. The Snake Demon hissed in pain, forced back by the sheer weight and heat of the Hashira's assault.
Tatsuya immediately moved Obanai further back. He stood guard, but his eyes were glued to the fight. He activated Silent Listening to its limit. He captured every rhythm: the roar of the fire, the pressure of the blade, the friction of scales on stone, and above all—Shinjuro's steady, furnace-like breathing.
He had never seen a Hashira fight this close. It wasn't just raw power; it was the art of perfect synchronization. Every swing of Shinjuro's blade carried a will that could incinerate anything.
The Snake Demon's eyes flashed with fear. It took a deep breath, its chest ballooning, and sprayed a thick, putrid green mist from its mouth—a high-pressure stream of poison aimed at Shinjuro's face!
"Blood Demon Art: Putrid Venom Breath!"
"Child's play!" Shinjuro roared, swinging his blade upward. "Flame Breathing, Second Form: Rising Scorching Sun!"
A geyser of fire erupted, vaporizing the poison mist instantly and leaving only the scent of ozone and char.
Failing again, the demon shrieked. Its body shook, and countless multicolored snakes shot out from between its scales and from the shadows—a rain of venomous serpents covering Shinjuro's entire space!
"Blood Demon Art: Heart-Devouring Myriad Snakes!"
Shinjuro didn't flinch. He spun his body in a perfect circle. "Flame Breathing, Fourth Form: Blooming Flame Undulation!"
A perfect ring of fire expanded like a shockwave. The lead snakes were carbonized instantly; the others were tossed back, burning and popping in the heat.
However, the demon wasn't trying to win; it was creating a gap. Its body suddenly wrinkled, and a foul liquid oozed from its scales.
"Blood Demon Art: Molting Decoy!"
With a violent surge, the demon's entire outer skin peeled off, remaining in place while a slightly smaller, faster "new" demon shot toward the secret tunnel entrance.
"Don't even dream of it!" Just as Shinjuro prepared to give chase, the "empty shell" left behind suddenly jerked to life!
Controlled like a puppet by invisible threads, the hollow husk inflated. Its empty sockets burned with ghostly green fire. The massive tail whipped through the air with a shriek, aiming for the back of Shinjuro's head. Simultaneously, the husk's mouth sprayed a dark green paralytic venom!
Shinjuro's momentum shifted. His fiery aura backflowed, creating a shield of heat.
BOOM!
The tail hit the fire with a dull thud, sparks spraying. The venom hissed as it hit the heat. Shinjuro sliced the decoy in half; the husk deflated like a punctured balloon and turned to ash.
The kill took only a second, but the true demon body was already gaining distance.
"Demon, is your whole soul dedicated to running? You won't succeed—!"
Shinjuro became a streak of fire, shrieking through the air as he pursued the monster into the depths of the estate.
Only a shout lingered in the air: "Slayer Tatsuya! Escort the boy out! There are Kakushi waiting in the cave—hand the rest over to them!"
"..."
Tatsuya stood in the plaza, staring blankly at the path of destruction.
From the Flame Hashira's grand entrance to the Snake Demon's desperate molting and escape, Tatsuya had watched the entire battle with absolute focus. To his shock, he realized that throughout that dazzling display of offense and defense, the Thunder Breathing within his own body had begun to circulate involuntarily.
His heartbeat, the rush of his blood, even the minute tremors of his muscles—all seemed to be pulled into resonance by Shinjuro Rengoku's fierce, surging, and life-affirming Flame Breathing.
He could clearly "hear" the power generated by the rhythmic expansion of the Hashira's lungs with every inhale, and the augmentation provided by the erupting spirit with every exhale. Unconsciously, Tatsuya's own breathing rhythm began to shift slightly to mirror the cadence of Flame Breathing. It was like a magnet being pulled and deflected by a stronger magnetic field.
"What's happening?!" Tatsuya thought, bewildered. "Why is my breathing being drawn to Flame Breathing? My body is moving on its own!" He tried to regain control, but the sense of harmony wasn't born of conscious mimicry; it was a deeper, primal pulse.
"This is different from the auxiliary warming effect of the Hinokami Kagura... this feels like a direct resonance between the Breathing Styles themselves."
His heart felt stronger than usual. With every pulse, his blood carried an unprecedented heat. It felt as though an invisible shackle had been removed—only a small change, perhaps, but it felt incredibly liberating. Even the range of his Silent Listening expanded; the rustle of the wind and the soft patter of falling snow in the distance became crystal clear.
Most importantly, his breathing rhythm had undergone a subtle, stable transformation. It was no longer just the explosive sharpness of Thunder Breathing; it had integrated a heavy, constant, furnace-like burn. The two rhythms coexisted and intertwined strangely within him, not clashing, but forming a more powerful, self-sustaining internal cycle.
"Is this right? I only wanted to learn from a Hashira's experience, but isn't this a bit too much of a surprise?"
Excitement replaced his confusion. He suppressed the urge to investigate immediately, but his gaze remained fixed on the path where the Hashira and the demon had vanished.
"I have to visit the Flame Hashira later, explain my situation, and ask for guidance! This feeling... it's amazing!"
The image of Jigoro Kuwajima's stern face flashed in his mind. With childish piety, Tatsuya quickly clasped his hands in prayer: "Master, I swear I'm not betraying Thunder Breathing! It's just... it seems I might... possibly... perhaps... also have a talent for Flame Breathing?! You can't blame me for that!"
"Hey! What are you dazing off for?!" Obanai's voice snapped Tatsuya back to reality.
"Sorry, sorry! Just thinking!" Tatsuya scooped Obanai up onto his back. "Hold tight! We can't stay here. Let's move!" Sparks of lightning flickered at his feet as he raced into the deep forest.
Within a few breaths, they had left the chaos of the estate behind, entering the silent, snowy woods. Tatsuya set Obanai down, and the two walked side-by-side.
"Alright, we're safe for now. Obanai, what do you plan to do next? Do you have anywhere else to go?" Tatsuya asked with concern. The boy had just escaped a cage and had no kin left.
Obanai's mismatched eyes flickered with complex emotions. He touched the jagged stitched scars on his mouth, his gaze falling on the "Slay" kanji on Tatsuya's uniform.
"I've already decided," his voice was raspy but clear, filled with a desperate resolve. "I'm going to join you."
"Join the Demon Slayers?" Tatsuya raised an eyebrow, not entirely surprised by the déjà vu.
"Yes. I can't go back to that disgusting family, and I have nowhere else to go. Kaburamaru is the only one I have." Obanai nodded firmly, then looked Tatsuya in the eye, his voice dripping with suppressed, icy hatred. "Tatsuya... what will the Corps do with the rest of the Iguro family?"
Tatsuya looked back at him and countered, "What do you think? They are technically your kin."
"Kin?" The stitched corners of Obanai's mouth twisted into a mockery of a smile. His gaze was like a blade. "They are not my kin! They are accomplices to a monster! Animals who sacrifice their own flesh and blood! Murderers who butcher travelers! They are... the ones who locked me up and raised me like livestock!"
He trembled with rage, every word forced through his teeth. "They all deserve to die! None are innocent! Their wealth, their 'family'—every inch is soaked in the blood of the innocent!"
Seeing the near-tangible hatred in the boy's eyes, Tatsuya remained silent for a moment before letting out a sharp laugh of agreement.
"Well said! I think they deserve to rot, too!" He spread his hands in a gesture of frustration. "Unfortunately, the Demon Slayer Corps isn't the police or the government. Our swords only slay demons, not humans—even when those humans are more poisonous than demons. We don't have the authority to judge them. Slaying demons is our job. Killing people? That's a whole different set of rules and headaches."
Tatsuya rubbed his chin, a thought occurring to him. "But... I can ask Kanae later. Her home is a Wisteria House; she has connections and good intel. Maybe she knows a way to contact officials who can handle this properly? Make sure those scumbags get what's coming to them."
Before Tatsuya could finish the sentence—
BOOM!
The snow nearby exploded! Frozen earth and snow shot into the air like a fountain.
"Hiss... my little delicacy... where do you think you're going?"
A cold, raspy voice, filled with mockery and greed, slithered into their ears like a viper.