**I.**
The days that followed settled into a rhythm more demanding than anything Muzan had known before, though Hikaru was careful, deliberately so, to keep that demand within limits a growing six year old's body could actually sustain.
Mornings began with the blade, the same set of basic stances repeated over and over, not for the sake of repetition alone but because Hikaru insisted, every single day, that form mattered more at this stage than speed or power ever could. "A fast strike built on a poor stance will fail you eventually," he told Muzan, more than once, adjusting the angle of his son's back foot for what felt like the hundredth time that week. "Better to be slow and correct now than fast and wrong later, when the mistake actually costs you something."
Muzan absorbed the correction each time with the same fierce, quiet focus he brought to everything, and though the stances themselves stayed largely the same from one day to the next, something in how he held them shifted, subtly, session by session, weight settling more naturally into his hips, his shoulders relaxing into positions that had felt rigid and foreign only days before.
"You're not just holding the stance anymore," Hikaru observed, midway through the second week. "You're starting to live in it. That's the actual goal. Anyone can copy a shape. Understanding why the shape works, and letting your body settle into that understanding rather than simply performing it, that's a different skill entirely, and a harder one."
---
**II.**
The stances themselves, Hikaru explained one afternoon, weren't chosen only for how they'd eventually translate into combat.
"Every stance in this set is built to engage a specific part of the body," he said, guiding Muzan through a low, wide legged position that pulled at muscles across his thighs and lower back in a way the earlier stances hadn't. "Core, legs, the small stabilizing muscles along your spine that most people never think about until they're missing. A shinobi who only trains the muscles he already notices ends up with gaps, weaknesses an opponent will find eventually, whether or not you ever bother to find them yourself first."
Muzan held the stance, arms trembling slightly with the effort of it, sweat beading along his hairline despite the relatively mild pace of the morning.
"This isn't about exhausting you," Hikaru added, watching him carefully for any sign the strain had crossed from productive into simply harmful. "I could push you considerably harder than this, and there'll be a time for that, later, once your body's had longer to build toward it. For now, the goal is familiarity. I want you to know every part of your own body this well, how it moves, where its weaknesses currently sit, long before I ever ask you to push those limits in earnest."
---
**III.**
Chakra work continued alongside the physical training, folded into the same mornings rather than set apart from them, and Suzu joined for a portion of most sessions now, her role shifting gradually from primary teacher to something closer to a second set of careful eyes, watching for any sign that Muzan's refining had begun outpacing what his growing body could safely support.
"Control, now, more than refining," she reminded him, one morning, as he sat in the familiar meditative posture between sets of stances, chakra gathering to his Hara in increments that had grown considerably steadier over the past weeks. "You have more to work with than you did a month ago. The temptation, at this stage, is always to reach for all of it at once, simply because you finally can. Resist that. Precision matters more than volume, every time."
Muzan nodded, and drew, carefully, exactly the amount she'd asked of him, no more, holding it steady at his Hara for a long, controlled moment before releasing it just as deliberately.
"Good," Suzu said, quiet satisfaction in her voice. "That's the actual skill. Not how much you can gather. How precisely you can decide."
---
**IV.**
It was several weeks into that same steady rhythm, Muzan's stances settling further into his body with each passing session, his control over each careful draw of chakra growing steadier by the day, when Hikaru decided the training had reached the point where words and correction from the sideline alone would no longer be enough.
"You need something better to measure yourself against than an old man correcting your footwork from the sidelines," Hikaru said, one morning, before Muzan had even fully finished his opening stretches. "I can tell you when your stance is wrong. I can't properly show you what it costs you against a real opponent, not without the gap between us making the lesson useless."
Muzan tilted his head, curious. "What do you mean?"
"I mean that sparring me right now would teach you nothing," Hikaru said, plainly, without unkindness. "It would be a small mound trying to measure itself against a mountain. The distance is too great to learn anything useful from the comparison. What you need is someone closer to your own height, so to speak, close enough that the gap actually teaches you something, rather than simply overwhelming you before the lesson even begins."
He gestured toward the training ground's entrance, where a young girl stood waiting, perhaps twelve or thirteen by Muzan's rough estimate, dressed plainly for training, her dark hair tied back with practical efficiency, watching the two of them with the patient, unhurried stillness of someone well used to waiting on instructions.
"This is Kaede," Hikaru said. "One of my subordinates, and one of the more promising young shinobi currently under my command. She's agreed to spend some of her mornings here, sparring with you, under my supervision. Treat the arrangement seriously. She's earned her skill, and you'll learn considerably more from losing to her honestly than you would from anything I could simply tell you."
Kaede stepped forward and offered Muzan a short, polite bow, the particular economy of someone who'd clearly been raised around proper training etiquette since long before Muzan had ever picked up a wooden sword. "I've heard a great deal about you," she said, something faintly amused in her tone. "Let's see if any of it holds up."
---
**V.**
The first exchange lasted less time than Muzan would have liked to admit.
Kaede moved with an economy that made his own still-developing form look, by comparison, exactly as unfinished as it actually was, closing the distance between them before he'd properly settled his footing, and though she pulled the strike well short of anything that would have actually hurt him, the wooden blade still tapped solidly against his shoulder before he'd managed anything resembling a proper defense.
"Again," Hikaru called from the sideline, not unkindly, simply matter of fact. "Muzan, your weight shifted too early. She read the tell before you'd even finished committing to the stance."
They reset. The second exchange lasted marginally longer, Muzan managing to deflect one strike before Kaede's second attempt found its mark regardless, and the third longer still, a real, if brief, exchange of blows before she slipped past his guard again.
"You're fast," Kaede said, between exchanges, genuine assessment rather than flattery. "Faster than most boys your age I've sparred against. Your form's still raw, but that'll come with time. The speed underneath it is the part that actually matters right now."
"You're better," Muzan said, matter of fact, without any particular sting of pride in the admission.
"I'm older, and I've had years you haven't had yet," Kaede said, resetting into her own stance. "That gap will close, or it won't, depending entirely on how seriously you take mornings like this one. Come on. Again."
Hikaru watched the exchanges with the same careful, quiet attention he brought to every part of Muzan's training, interjecting corrections at precise moments, adjusting Muzan's grip mid-exchange, calling out the exact instant Kaede's footwork shifted to signal an incoming feint so Muzan could learn to read the tell himself in future rounds.
"Watch her shoulders, not her blade," he called out, during one particular exchange. "The blade moves last. The shoulders tell you where it's going before it ever gets there."
Muzan adjusted, and the next exchange lasted longer still, his own strike actually connecting, lightly, against Kaede's guard before she recovered and pressed the advantage back in her own favor.
"Better," Kaede said, something like genuine approval in her voice now, stepping back to reset the distance between them. "You listen well. That's rarer than you'd think, at your age."
By the session's end, Muzan was breathing hard, sweat soaked through his training clothes, his arms aching in a way that felt, somehow, more honest than the ache from repetition drills alone, the particular exhaustion of having actually been tested rather than simply having practiced in isolation.
"Same time tomorrow," Hikaru said, as Kaede offered Muzan a final, respectful bow before excusing herself to whatever other duties awaited her that day. "You'll spar with her most mornings, going forward, alongside your other training. I want you measuring your progress against something real, not just against yesterday's version of yourself."
Muzan nodded, still catching his breath, already turning the morning's lessons over in his mind, the shoulder tell, the timing of her feints, the small gap in her guard he thought he'd almost found on that last exchange before she closed it again.
"I'll close the gap," he said, quiet, more to himself than to either of them.
Hikaru, watching him, allowed himself a small, private smile, the particular satisfaction of a teacher watching a student find, entirely on his own, exactly the kind of determination no lesson could properly teach from the outside.
"I don't doubt you will," he said. "Just don't rush it. The gap closes on its own time, not on however fast you'd like it to."
---
**VI.**
By early afternoon, the pace eased deliberately, Hikaru drawing the physical training to a close well before exhaustion could tip over into anything genuinely harmful, and Muzan, still faintly sweat damp and pleasantly sore in the particular way honest work leaves a body, was handed back over to whichever lesson the day's schedule called for next, chakra theory some days, the slow, patient unspooling of clan history and regional politics on others.
"You'll thank me for this pacing eventually," Hikaru told him once, catching the faint flicker of impatience that occasionally crossed Muzan's face when the morning's training ended before he felt properly finished with it. "A shinobi who trains himself into the ground every single day burns out long before he ever reaches his actual potential. Better to build steadily, session after session, than to chase a false sense of progress that costs you more than it gives back."
Muzan, still catching his breath, nodded, and though some restless, eager part of him privately wished the mornings could stretch longer, a quieter, more patient part, the part that had spent a great deal of time recently turning strange and heavy realizations over in careful, deliberate silence, understood, better than most children his age ever could, exactly why the pacing mattered as much as his father insisted it did.
The afternoons that followed passed more quietly, scrolls and maps and careful, measured conversation replacing the sweat and strain of the morning, and if Muzan occasionally found his attention drifting, just slightly, toward the mark on the back of his hand, and everything still waiting, unopened, inside it, he kept that particular restlessness carefully to himself, for now, content to let his training, all of it, chakra, blade, and whatever else still lay ahead, unfold at the pace his father had chosen, one deliberate step at a time.