- Several days later.
Kagerou sat alone on the engawa, a kiseru resting loosely between his fingers.
Normally, a single puff of smoke was enough to calm his mind.
But not today.
Not these days.
His head leaned against one of the wooden pillars, eyes unfocused as he stared at the quiet garden. The sounds of the estate drifted past him without meaning. The wind rustled through the trees.
Kagerou heard none of it.
Over the past few days, Kagaya had issued a mission for him.
But after seeing Kagerou's condition, Shinjuro had refused it on his son's behalf.
In the Demon Slayer Corps, refusing a mission was no small matter. The Corps was a strict organization. Such actions could lead to punishment, demotion, or even being judged unfit for duty.
So Shinjuro had personally gone to the Ubuyashiki estate to explain the situation.
Unexpectedly, Kagaya had not been angry.
Instead, after hearing what had happened, Kagaya simply laughed.
Not just him.
Even Amane had been smiling beside him.
In the end, Kagaya granted Kagerou leave until his condition improved.
What Kagerou's reaction would be when he learned about it later was something no one could predict.
Back at the estate, Kagerou slowly exhaled a thin stream of smoke.
The more he thought about it, the heavier the feeling became.
There was no blood.
No visible wound.
Yet every day, the pain inside his chest grew stronger, as if something were slowly tearing him apart from the inside.
He hadn't expected the impact to be this severe.
That day, he had only thought about telling Kanae the truth.
He had even made her promise that things wouldn't change between them afterward.
But he had never considered that the weight of that truth might crush him instead.
Before leaving for his first official mission, Kagerou had already decided something.
Kanae was special.
Someone he could trust... Someone he could rely on without hesitation.
Just like his mother once told him, in this cursed world, he would need someone he could entrust his life to.
That was what Kanae had become to him.
After all, they had survived the Final Selection side by side.
But he hadn't realized something important.
Kanae was more than that.
He only understood it after everything had already fallen apart.
Shinjuro had been right.
There were things that could never be learned through talent alone.
Swordsmanship.
Breathing techniques.
Battle instincts.
Those could all be mastered with talent.
But understanding the human heart… That was different.
Only now did Kagerou finally understand that. And by the time he did… It might already be too late.
A quiet sigh escaped his lips as he tilted his head back, his gaze drifting toward the pale sky above.
"…Mother," he murmured softly. Ruka's gentle face surfaced in his mind. "What should I do in this situation?"
---
Not far from where Kagerou sat
Kyojuro, Senjuro, and Obanai stood in the training yard, listening attentively as Shinjuro instructed them on breathing techniques.
Kyojuro and Senjuro had already mastered the basics. What they needed now was simply to strengthen their foundations.
Because of that, Shinjuro's attention was mostly focused on Obanai.
"…Obanai," Shinjuro said firmly, his arms crossed over his chest. "The first thing every Demon Slayer must learn is Total Concentration Breathing"
He glanced at the three boys before continuing.
"Without mastering this, everything else is meaningless"
Shinjuro stood with his arms crossed, his sharp eyes fixed on the boy before him.
"The sword techniques you see, Flame, Water, Thunder, all of them, are merely expressions of breath. If your breathing collapses, your form collapses. If your breath wavers, your blade wavers"
He took a slow step forward.
Obanai straightened instinctively under the pressure of his gaze.
"You must learn to control the air that enters your lungs, guide it through your blood, and carry it into your muscles. Only then will your body move the way a Demon Slayer's body should"
Shinjuro raised two fingers.
"Inhale"
Obanai obeyed immediately.
"Not like that"
Shinjuro's voice cut in sharply.
"You are breathing with your chest. That is shallow breathing. It will exhaust you in minutes during battle"
He placed a hand over his own abdomen.
"Breath begins here. Draw the air deep into your lungs until your diaphragm expands. Fill your body, not just your chest"
Obanai tried again, slower this time.
"Inhale… hold… and release"
A thin stream of breath escaped Obanai's lips.
Shinjuro watched silently for a moment before nodding slightly.
"Better"
Beside them, Kyojuro stood with his usual bright posture, observing with keen interest, while Senjuro mirrored the breathing pattern quietly, trying to follow along even though the lesson was not directed at him.
Shinjuro continued.
"Breathing is the foundation of everything we do. When you fight demons, fear will tighten your chest. Pain will disrupt your rhythm. Your mind will try to panic," His gaze hardened slightly. "And the moment that happens, that's when it all ends"
He lowered his hand.
"That is why Total Concentration Breathing must become second nature. Once you can maintain this breathing without thinking, we move to the next stage"
His eyes sharpened.
"Breathing not only during training… but every second of the day"
Obanai's eyes widened slightly.
"Walking. Sleeping. Eating. Even when your mind wanders"
Shinjuro turned away slightly, looking toward the distant mountains.
"A demon does not wait for you to catch your breath," he said quietly. "So if your breathing fails… You die, remember that"
Silence followed.
Only the steady rhythm of controlled breathing remained between them.
"Inhale," Shinjuro ordered again. "And do not stop"
"Understood, Shinjuro-san," Obanai replied quietly.
"Good," Shinjuro said with a small nod of approval. "You started later than the others. That means you must work harder than everyone else"
After saying that, Shinjuro shifted his attention to Kyojuro and Senjuro.
"And you two… why are your hands not moving?"
Kyojuro and Senjuro had both been staring toward the engawa where Kagerou sat alone. At their father's voice, they quickly turned their attention back to him.
"…Father, is it really okay to leave Kage-nii like that?" Kyojuro asked.
Hearing this, Shinjuro swept his gaze toward his eldest son before letting out a quiet sigh.
"There's nothing we can do," he said before looking back at the two boys. "He caused this himself. He has to solve it himself"
"But-"
"Enough"
Shinjuro's voice cut sharply through the air.
"There's no need for you two to worry about your brother. Worry about yourselves instead. At this rate, you'll never catch up to him"
He waved a dismissive hand.
"Continue your training. I'm going to the market to buy a few things"
He paused briefly before adding,
"And don't be lazy"
With that, Shinjuro walked away. As he passed the engawa, he glanced once at Kagerou, then shook his head slightly before continuing down the road.
Kyojuro and Senjuro watched their father leave.
Then they both looked toward their older brother again.
Kagerou still hadn't moved.
A thin trail of smoke drifted slowly upward from the kiseru in his hand.
After a moment, the two brothers reluctantly returned to their training.
---
Not long after
"…Senjuro. Obanai," Kyojuro suddenly said. "We need to do something. We can't let Kage-nii stay like that"
"…But what should we do, Nii-san?" Senjuro asked.
"Hmmm"
Kyojuro closed his eyes thoughtfully, placing one hand under his chin.
A moment later, his eyes suddenly opened.
"I know!"
"Should we go find this 'Kanae' and explain Kage-nii's situation?"
"That's a good idea, Kyojuro-san," Obanai replied.
"Right-"
"But"
Obanai tilted his head slightly.
"Do we actually know what this Kanae looks like… or where she lives?"
"…."
"…."
Kyojuro's confident expression slowly froze.