Pulling Juliet out of his box once more, Goku handed the letter to the owl. He hopped onto the Flying Nimbus and followed her, soaring westward through the night sky.
Meanwhile, in the Yoshiwara Entertainment District, the man disguised as a common courtesan was trembling—not just with rage, but with a primal, icy fear. The fact that seven Upper Moons had been wiped out in a single blow meant the boy truly had the power to kill him.
Even without the bloodline suppression he held over his minions, Muzan knew he couldn't one-shot all his Upper Moons simultaneously.
The boy's strength was potentially greater and more terrifying than even Yoriichi Tsugikuni, the man who had haunted in his nightmares for centuries.
'From this moment on, I am simply the courtesan, Mai,' Muzan decided. He planned to live as an ordinary woman in the district for the next few hundred years if necessary. He would wait until the boy aged and died before ever showing his face as Muzan Kibutsuji again.
He chose the identity of an oiran because it provided the perfect cover: they slept during the day and worked at night, explaining away his demonic lifestyle. Most importantly, in a crowded city, he could use fragile humans as shields to create openings for escape—a tactic he knew the "righteous" Demon Slayers couldn't counter.
"You will eventually die... everyone dies..." he hissed to himself.
"Found you, Muzan Kibutsuji!"
At midnight, amidst the brilliant lights of the Yoshiwara district, Goku sat atop his Nimbus and gently caught Juliet as she began to descend. Although Muzan had escaped him at the castle, Goku had memorized his ki. As long as Muzan was within a fifteen-kilometer radius, there was nowhere to hide.
"It wouldn't be good to fight down there," Goku muttered, looking at the dense crowds. He began to chant.
"Cave Inimicum!"
His figure gradually blurred and vanished under the effects of the Disillusionment Charm.
Suppressing his aura entirely, Goku Apparated onto the roof of a brothel and slipped silently into a private room. He paused for a moment; instead of the short-haired man he'd seen at the castle, the room contained an unremarkable, long-haired woman.
However, after closing his eyes to sense the ki, Goku knew he hadn't made a mistake. Features could be altered, but the essence of one's soul—their ki—was constant. He had learned this from Nymphadora Tonks; no matter what shape her Metamorphmagus abilities took, her ki remained the same.
In a blur of speed, Goku lunged at the "woman."
"Something's wrong!"
Muzan, currently folding clothes, felt a sudden surge of unease. He looked around but saw nothing. Yet, the sudden crack of a sonic boom near his ear alerted him to an invisible strike. He abandoned his disguise instantly. His arms transformed into horrific, barbed whips, lashing out at the source of the sound.
The whips broke the sound barrier, but because Goku had the initiative, the attack missed.
Muzan felt a hand grip his shoulder. Before he could react, the scenery shifted violently. He was back inside the wooden halls of his own Infinity Castle. His shoulder sprouted a fanged maw to bite the hand holding him, but it snapped at empty air.
"Muzan Kibutsuji, now we can have a proper duel!"
Goku cancelled the Disillusionment Charm, revealing himself five meters away.
Looking at the familiar environment and the boy's battle-ready stance, Muzan roared with desperate, forced bravado: "You think finding me means you can kill me? Even Yoriichi Tsugikuni failed to finish me! You are nothing!"
Muzan knew there was no more running. The boy had a way to track him across the world. He had to kill him. He wanted to live; he wanted to conquer the sun and become the perfect being. Anyone in his way had to die.
"DIE!"
His arms, now barbed whips, lashed out with savage ferocity. Simultaneously, nine tube-whips erupted from his back, sealing off every possible escape route. Each strike carried the force of a sonic boom.
Facing an onslaught more ferocious than all the Upper Moons combined, Goku's eyes sparkled with excitement. This was the opponent he had been looking for.
"Breath of Ki, First Form: Flowing Impact!"
The attack that had erased the Upper Moons returned. Goku moved like water, his fists meeting both the arm-whips and the nine back-whips. In a series of concussive explosions, Muzan's appendages were reduced to mincemeat.
"GO TO HELL!"
Muzan wasn't surprised. He had seen this move through the dying memories of his Upper Moons.
*SHING!*
Eight additional tube-whips suddenly burst from Muzan's legs, striking upward from the floor toward Goku's midsection. This was his true ace. The arm and back whips had been mere bait; these leg-whips were faster and far more lethal.
Goku was momentarily surprised by the subterranean ambush, but his battle instincts were peerless. He leaped high into the air, narrowly dodging the thrusts. But the whips were under Muzan's total control; they twisted in mid-air, pursuing Goku into the sky.
"Dodonpa!"
Goku's finger flicked eight times. Eight beams of orange light shot out with pinpoint accuracy, vaporizing the leg-whips instantly.
Muzan's expression darkened. "So what? I have plenty more! Let's see who runs out of energy first!"
In the blink of an eye, the whips regenerated. As the progenitor of demons, his recovery speed was leagues beyond his subordinates. Unless he faced the sun or every single one of his cells was destroyed at once, he was immortal. He planned to grind the boy down, waiting for the moment his human stamina finally failed.
If the boy tried that giant energy beam again, Muzan would simply dodge. If the Upper Moons could evade it, he certainly could.