Muzan knelt next to Michikatsu in the cave's shadows.
"I must explain what will happen," Muzan began. "What I've become."
Michikatsu turned his sightless eyes toward him. "I'm listening."
"I'm no longer fully human. I'm stronger than anyone should be, faster than you can imagine. In total darkness, I see perfectly. I can also reshape my body at will." Muzan hesitated. "But there's a price. Sunlight incinerates me. Just a few minutes, and I'd be dead."
"That's impossible."
"I thought so too. But here I am." Muzan adjusted his posture. "I believe I can do the same for you. My blood has the same transformative properties as what changed me. If you drink enough of it, you should change like I did."
"You've never tried this before."
"No."
"So, you have no idea if it will actually work."
"I don't."
"And if it fails?"
"You die. Likely in agony."
Michikatsu's scarred face betrayed no emotion. "At least that would be quick. Better than wasting away in this cave for forty more years." He leaned back against the stone. "Go ahead."
Muzan sharpened a fingernail and opened his wrist, dark blood seeping from the cut.
He pressed the wound to Michikatsu's mouth. "Drink as much as you can."
Without hesitation, Michikatsu closed his lips around the cut and swallowed in steady gulps, while Muzan felt chakra draining from his own body.
After the fifth swallow, Muzan withdrew. The wound quickly sealed itself.
"Do you feel—"
Suddenly, Michikatsu convulsed violently.
His spine arched, leaving only his shoulders and hips on the ground, his skull crashing against the stone wall. His mouth opened in a silent scream as his vocal cords locked.
Muzan watched helplessly as Michikatsu thrashed and the stumps where his limbs had been jerked unpredictably.
Then the transformation began.
His skin rippled like liquid. Old scars disappeared, replaced by fresh tissue.
His empty eye sockets glowed with pulsating red light emanating from within his skull.
Bones cracked and restructured as his skeleton morphed into something new. His jaw pushed forward, lengthening, and his cheekbones elevated into sharper angles.
The stumps of his arms extended, white bone materializing first, followed by muscle that wrapped tightly around it, tendons flawlessly connecting everything. Skin stretched over it all, forming long forearms and hands with individual fingers that flexed as they finished growing.
A similar process occurred with his legs, as bone pushed out, muscle developed, and skin enveloped the structure. Feet formed from nothing, toes pressing firmly against the cold stone.
The birthmark on his forehead began to spread. Every Tsugikuni bore one, and this flame-like pattern twisted down the left side of his face, resembling veins or roots. Additional marks appeared on his right cheek and descended his neck in intricate branches, pulsing in time with his heartbeat before settling into a deep crimson against his increasingly pale skin.
His hair lengthened, reaching his shoulders, transforming from black to deep red at the tips.
Then, impossibly, his face split open.
New eyes emerged where there shouldn't have been any—six in total, arranged vertically in three pairs down his face. The center pair was positioned normally, glowing brightest with yellow irises surrounded by red. Black lines radiated from each pupil like spokes. The upper pair of eyes rested where his eyebrows had been, while the lower pair sat on his cheeks. At first, all six eyes moved independently, but then they focused on Muzan simultaneously.
The convulsions finally ceased, and Michikatsu established a steady breathing rhythm.
Slowly, he raised his right hand in front of his face, all six eyes fixated on it. He flipped his hand over and flexed each finger in turn.
"I can see." His voice was now deeper and rougher. "I can truly see everything."
Pushing himself upright, he took cautious steps on his newly formed legs. Despite the unfamiliarity, his movements were deliberate and controlled.
"I can move again. Walk on my own."
He brought both hands to his face, tracing the new markings with his fingertips and exploring the extra eyes.
"What have you made me into?"
"A demon. The second one in existence, as far as I know."
The weight of his gaze settled on Muzan, unsettling in its intensity.
"I can feel it within me. In my muscles, my bones. Each drop of blood." His voice remained steady. "I'm stronger than I've ever been."
He clenched his fists, muscles standing out sharply.
"Strike something," Muzan urged. "Test your new abilities."
Michikatsu faced the nearest cave wall, drew his fist back, and struck the stone with all his force.
The wall erupted on impact, debris flying and forming a crater the size of a barrel. Cracks radiated from the point of impact in perfect geometric lines.
He inspected his knuckles, untouched.
"Impressive."
"There are critical things you need to understand about this transformation," Muzan replied quietly.
Michikatsu narrowed all six eyes. "Tell me."
"You won't be able to consume normal food anymore. It will make you ill—possibly fatal. Your body can only process human flesh, and it's more effective if they possess chakra."
"So I have to eat people to survive."
"Yes."
Approaching the cave entrance where sunlight streamed in, Michikatsu hesitated at the threshold and thrust his hand into the light.
His skin began to smoke immediately, charring and cracking like burned meat.
He withdrew his hand quickly, watching as the burns healed within moments.
"I would die if I stepped out there."
"You would."
Gazing at his healed hand, all six eyes observed his fingers' subtle movements. "Yet everything else returned. My arms, my legs, my eyes—all regenerated."
"Your body operates differently now. You can heal from nearly anything, regenerate lost parts, and alter your shape if you concentrate."
"Show me how to change shape."
Muzan concentrated, his flesh shifting and transforming into long bladed whips.
"Once you grasp the concept, it becomes second nature."
"I want to try."
Focusing on his right hand, Michikatsu watched as the flesh flowed like liquid, forming a katana blade at his wrist.
He inspected the weapon with all six eyes. "The balance is perfect. Better than any sword I wielded when I was human."
"We should test your capabilities, but with caution."
They moved to the cave's widest section, where the ceiling soared.
Settling into a familiar sword stance, Michikatsu positioned his feet with precision, distributing his weight mathematically, all six eyes trained on different areas of Muzan's body.
Muzan held his whips loosely at his sides.
Without warning, Michikatsu attacked.
His blade struck swiftly, aiming for Muzan's abdomen with inhuman speed.
Muzan dodged, feeling the air stir as the blade passed close.
Michikatsu quickly followed with a diagonal slash.
Muzan's left whip hardened to catch the blade, the scrape of metal against metal resonating in the cave.
Michikatsu pressed forward, forcing Muzan to slide back two steps before regaining his balance.
"You're faster than I expected," Muzan admitted.
"This body moves better than my previous one." Michikatsu adjusted his grip. "Everything feels more efficient."
He lunged at Muzan again, landing three quick strikes—high, middle, low.
Muzan blocked the first two but had to leap back to evade the third.
Michikatsu closed the distance with a single step and thrust the blade toward Muzan's chest.
In a swift motion, Muzan twisted to the side. The blade grazed his ribs, leaving a shallow cut that began healing instantly.
His right whip shot out, ensnaring Michikatsu's sword arm.
Instead of trying to escape, Michikatsu transformed his left hand into long, curved claws that glimmered in the light.
He raked them across Muzan's shoulder, cutting deep to the bone.
Muzan released his grip and retreated several paces, both their wounds closing within moments.
"You're adapting quickly."
"It doesn't feel like learning. It's as if my body knows what to do instinctively," Michikatsu mused, inspecting his clawed hand with fascination. "The intent solidifies in my mind, and my body responds before I fully think it."
He charged forward, coordinating sword strikes with claw swipes, alternating seamlessly, forcing Muzan to focus entirely on defense.
His whips worked together in intricate patterns, attempting to block the dual assaults. The rhythm shifted unpredictably, complicating Muzan's anticipation.
Those six eyes granted Michikatsu a significant advantage; each pair monitored different aspects. One set tracked movement, another focused on hand positioning, while the last observed Muzan's shifts in weight, providing him insight into Muzan's next actions.
Muzan accelerated, his whips blurring with speed.
Michikatsu managed to deflect most strikes, with only two getting through, creating shallow cuts on his arms that healed before blood could fall.
They circled each other, steadying their breaths after the intense exchange.
"You're holding back," Michikatsu said.
"So are you."
"I'm still unraveling my new capabilities."
"Then let's discover them for real."
Muzan launched an assault with both whips aimed at him—one for his head, the other for his legs.
Michikatsu caught them, pulling hard in opposite directions.
Muzan stumbled as his balance faltered.
With a swift knee strike, Michikatsu struck Muzan's chest, pushing the air from his lungs.
Muzan ensnared both whips around Michikatsu's arms, pulling with all his might. They collapsed to the ground, quickly rolling apart.
Both regained their footing in fighting stances.
"Better," Michikatsu remarked. "But your technique is still rough. You rely too heavily on speed and strength instead of proper form. Your movements lack refinement."
"I've never practiced with a sword."
"I can tell." Six eyes scrutinized him intensely. "But you possess raw talent. Your body has the tools needed; you just need to learn how to wield them properly."
Michikatsu flowed through a series of cuts, each leading seamlessly into the next, every step of his footwork positioning him perfectly for the following strike.
"Try to mimic my motions."
Muzan attempted the sequence, feeling awkward and out of sync.
"You're overthinking each move instead of letting them flow together naturally. Your body knows how to move efficiently. Stop forcing it; just allow it to happen."
Muzan tried once more, this time focusing less on perfection and more on maintaining fluidity.
It felt improved.
"Again."
He repeated the sequence five more times, each iteration growing smoother as his body adapted to the rhythm.
"Good enough. Now, defend."
Michikatsu attacked with straightforward combinations that clearly indicated his intent.
Muzan's whips moved instinctively, blocking all three strikes without conscious thought.
Then Michikatsu intensified his efforts, adding feints and altering timings to confuse Muzan's predictions.
Muzan successfully defended against most of the onslaught, but a couple of strikes broke through, leaving shallow cuts that healed almost instantly.
They continued for another twenty minutes, Michikatsu providing real-time corrections to Muzan's form, guiding his foot placement and weight distribution, teaching him to let movements cascade into one another without wasting energy.
Eventually, they paused, facing each other, both unmarred despite the intense duel.
"I never thought I'd experience this again," Michikatsu admitted, his voice steady but tinged with satisfaction. "I presumed that part of my life was permanently over."
"You may very well be the best swordsman alive now."
"That's still not enough." His six eyes glowed with fierce determination. "I will become stronger, faster, and more skilled. I want shinobi to hear my name and feel the same fear as if death itself were approaching."
"Is that truly your desire?"
"I aim to improve without limits, to never stop." His eyes shone even brighter. "But first, Shinji must be dealt with. He's shown he's unworthy of leadership."
He transformed his sword hand back to normal fingers, flexing them.
"But you deserve it. You should reclaim what was taken from your family. Rule the Land of Iron. Command all demons. Be the Demon King."
"That is my intention."
Michikatsu leaned against the cave wall. "So what's your actual strategy for dealing with Shinji? I assume you won't simply kill him and take over."
"No. Such a move would be too simplistic, too crude."
"Wise." He nodded slightly. "Possessing overwhelming power means little without knowing when to wield it and when to restrain. That distinguishes true leaders from mere destroyers."