- Twenty Days later.
The backyard of the Rengoku residence was usually bright and warm, basking in sunlight from morning until late afternoon.
Today, it looked like a battlefield.
Thick smoke devoured everything. It clung low to the ground, curled upward in shifting layers, and blurred the world until even an outstretched hand appeared only as a vague silhouette.
Kyojuro, Senjuro, and Obanai stood shoulder to shoulder, all three sweating, all breathing in controlled, deliberate rhythm as they tried to sense their surroundings without relying on their eyes.
Kyojuro's bright grin hadn't faded.
If anything, it burned even stronger the more impossible the situation became.
"…Obanai, how is it?" he asked, closing his eyes in an effort to widen his perception.
Obanai didn't answer immediately. Kaburamaru's head swayed left and right, tongue flicking rapidly… But there was nothing to find.
Kagerou's smoke didn't just obscure. It distorted depth, muffled vibrations, and ate sound. It was like a living mist.
Finally, Obanai spoke:
"…Nothing. Kaburamaru senses nothing"
There was no panic in his voice.
Ever since his quiet talk with Kagerou that morning, Obanai had been following the older man's words, slowly starting the path toward becoming a Demon Slayer.
At first, it was only stamina training.
But today, when Kyojuro suddenly announced he wanted a mock battle with Kagerou... somehow both Senjuro and Obanai were dragged into the fight.
"Hahaha! This is troublesome!" Kyojuro boomed, steam practically rising from his body as he pushed his breathing deeper. "Even my Flames struggle to carve through this haze!"
Senjuro wiped sweat from his chin, blinking rapidly as the smoke stung his eyes.
"Brother… this is way worse than before. Kage-nii keeps increasing the smoke's density…"
Kyojuro nodded, thrilled. "Indeed! A marvelous challenge!"
Obanai's brows furrowed.
"…He's close"
Senjuro stiffened. "Eh?! Where?!"
"I don't know." Obanai tightened his grip on his wooden blade. "He's hiding within the smoke itself. Right at the edge of our senses"
Kyojuro inhaled, focusing. "Then-"
A swirl of smoke twisted behind them.
Kyojuro snapped around... Nothing.
Another faint brush of movement skimmed past Obanai's right shoulder.
He slashed toward it... Nothing again.
Senjuro gulped, voice trembling. "H-He… he vanished again…"
Kyojuro's eyes lit up with pure exhilaration.
"Kage-nii! Your stealth is incredible!"
Somewhere unseen, beyond the layered veil of smoke, a faint chuckle drifted through the air, soft, low, almost teasing.
Then, from every direction at once:
"Not bad… but you're still too tense"
All three froze.
The voice felt close.
Very close.
Obanai's pulse jumped, and before any of them could react... A gentle tap landed on each of their shoulders.
Simultaneously.
The three boys whipped around in shock.
Kagerou stood behind them casually.
Calm smile.
Half-lidded eyes.
Kiseru resting loosely between his fingers.
"You'll never sense me," Kagerou said, exhaling a thin ribbon of silver smoke that vanished the moment it touched the air. "If you keep relying on your eyes-"
"Now!!"
Kyojuro's roar split the haze as he lunged, blade slicing a bright arc toward Kagerou's head.
Senjuro followed a heartbeat later, striking low.
Obanai moved last, fast and precise, aiming for the blind spot.
Three strikes.
Three angles.
Perfect timing.
And Kagerou... Kagerou didn't move.
He only smiled.
Their blades connected with nothing.
No flesh.
No resistance.
Only air.
All three froze.
"!!!"
"What!?"
"This… isn't real…?"
"Another illusion?" Obanai whispered, eyes wide behind his bandages.
A quiet snort answered them.
"Pfft~ Didn't I tell you?" The voice came from behind, lazy and amused. "Don't rely on your eyes"
The smoke around them thinned, swirling away like it had never been there.
And there he was.
Kagerou leaned casually against a tree trunk, kiseru resting in the corner of his mouth, half-lidded eyes studying them as if assessing children playing with sticks.
"You guys," Kagerou said, exhaling another slow, silver trail of smoke, "still have a long way to go"
"Kage-nii! Since when?!" Kyojuro blurted, eyes blazing with shock and admiration.
"Huh?" Kagerou tilted his head, genuinely confused. "Since the beginning. I've always been here. Never moved"
He pushed himself off the tree and walked toward them, his footsteps quiet, steady, unhurried. When he stopped in front of the three, the air felt heavier, not from intimidation, but from the undeniable gap in skill.
"I think that's enough for today," he said calmly. "You still have many things to learn. Especially you, Obanai. You started late, so you'll need to work the hardest"
Obanai stiffened, his fingers curling around his wooden sword, but he nodded without a word.
"Kyojuro," Kagerou continued, turning his gaze toward his little brother, "you need to learn how to stay calm. Don't rely only on your senses. Sometimes… you have to trust your instincts more than your eyes or your ears"
Kyojuro's fire wavered, embarrassed, but eager. "Y-Yes! I'll work on it!"
"And Senjuro…" Kagerou's gaze softened slightly. "I'll talk to Father later. It's time for you to learn a Breathing Style"
Senjuro's eyes widened instantly, face lighting up like the sun. "R-Really, Kage-nii?!"
"Yeah," Kagerou said, a small smile tugging at his lips. "Really"
"Kage-nii-" Kyojuro's voice shot up. But Kagerou cut him off with a raised hand.
"Kyojuro. What did I tell you before? Master Flame Breathing first"
Kyojuro froze, then deflated with a defeated sigh. "…I understand."
Silence settled over them.
But not a heavy one.
A thoughtful one.
Obanai's hands tightened. He didn't complain. He didn't protest. But inside… he knew exactly where he stood.
His body, weak. His training, late. His stamina, poor.
He wasn't even at Senjuro's level.
So he stayed quiet.
Because he knew he had no right to ask for a Breathing Style yet.
Kagerou glanced at him briefly.
Saw the frustration.
The longing.
The fear of being left behind.
But he didn't say anything, for now.
He simply let the smoke drift from his kiseru, letting the breeze take it wherever it pleased.
"Alright," Kagerou said, flicking the ash from the pipe, "go clean yourselves"
The three younger boys nodded immediately.
"Alright! Let's go!" Kyojuro declared with his usual blazing enthusiasm, throwing an arm around Senjuro and Obanai's shoulders in a single sweeping motion.
Senjuro stumbled forward with a laugh. "Brother, too strong! Too strong!"
Obanai stiffened at first, caught off guard by the sudden physical contact… but he didn't pull away. Not this time. Kaburamaru flicked its tongue at Kyojuro in mild confusion, but it didn't bite.
Together, the three walked toward the house, Kyojuro practically dragging them, Senjuro smiling brightly, and Obanai looking like he wasn't sure how to handle this kind of warmth at all.
Kagerou watched them go.
Their voices faded into the hallway, loud and youthful. The kind of sound most people would take for granted.
He let out a slow, thoughtful breath, smoke curling upward.
"…Good," he murmured to himself, eyes softening. "They've become closer and stronger"
But his gaze lingered on Obanai's small back the longest.
There were things that the child still didn't know about himself.
Things he would need to face soon.
And Kagerou already knew: He would be there when that day came.