"Breath of Ki, First Form: Flowing Impact!"
Goku was well aware of Muzan Kibutsuji's strategy of attrition, but he was in no hurry to strike at the demon's core. Instead, he continued to use his newly realized Breath style to sweep away the incoming barbed whips and tube-whips.
By the third time he executed the form, it felt significantly more natural than the first. Its destructive power grew as his movements became more refined. Muzan wanted to drain Goku's stamina, but Goku was using Muzan as a high-level training partner to polish his new techniques.
To him, only Muzan possessed the strength necessary to provide a proper challenge.
The fourth time, the fifth... the eighth, the ninth.
By the time Goku unleashed the First Form for the tenth time, Muzan realized with a jolt of horror that his regeneration was failing to keep pace. The speed of the boy's strikes was accelerating.
"Breath of Ki, First Form: Flowing Impact!"
On the eleventh iteration, just as the whips were vaporized, Goku's fist followed through. Before Muzan could even process the movement, a fist packed with a mountain of ki slammed into his chest. The Demon King's body instantly detonated into a cloud of crimson fragments.
But Muzan was the progenitor of all demons. Even as a cluster of gore, he didn't lose his will to kill. His blood coalesced mid-air into a single, massive whip of solidified ichor, lashing out at Goku with a vengeful roar.
"Die! Blood Demon Art: Black Blood Brambles!"
This whip was concentrated from the majority of his demonic blood. Its speed and piercing power were several times greater than any of his previous attacks—it was his ultimate trump card for a counter-kill after being heavily wounded.
"Breath of Ki, Second Form: Bursting Gale Slash!"
Goku landed and used the edge of his hand like a blade. Drawing inspiration from the Wind Breathing he had learned from Sanemi, he unleashed thousands of invisible slashes in a split second. Dense, pressurized blades of ki swarmed the air.
The massive blood-whip didn't last three seconds before it was diced into a fine mist of blood droplets that fell harmlessly to the floor.
After perfecting his First Form based on Water Breathing, Goku had successfully adapted the gale-like ferocity of Wind Breathing into his Second Form.
"This is bad!"
The scattered chunks of Muzan's flesh, unable to regroup, watched the incoming storm of ki blades with sheer terror. If these hit, every single fragment of his body would be annihilated. He would be erased from existence.
"NO!"
Driven by the ultimate instinct for survival, Muzan unleashed his most desperate technique—one he had spent centuries developing specifically for a moment like this.
"Blood Demon Art: Explosive Shockwave!"
A massive, invisible wave of kinetic energy erupted from the center of Muzan's scattered remains. The surrounding wooden structures of the Infinity Castle were instantly ground into dust. Even with Goku's superhuman constitution, the direct impact of the shockwave caused his entire body to seize up and stiffen.
The shockwave dissipated the majority of the ki blades. Although many flesh fragments were still destroyed, enough remained for Muzan to forcibly pull himself back together.
He stood there, gasping for breath, his form flickering. He was more weakened now than he had been after his legendary defeat by Yoriichi. But he didn't stop. He lunged at the paralyzed Goku.
That shockwave wasn't just physical; it was designed to assault the human nervous system, causing temporary paralysis. The boy's physical body was too strong for simple wounds, but his nerves were still human—and the shock had worked.
Muzan's right hand transformed into a giant, fanged maw, intending to swallow Goku whole before he could recover.
However, he had underestimated the sheer resilience of a Saiyan's biology. Just as the maw reached him, Goku's eyes snapped open.
"Petrificus Totalus! Petrificus Totalus! Petrificus Totalus!"
Goku launched a rapid-fire barrage of punches. Curiously, he didn't use much physical force; instead, he focused entirely on sheer speed. With every hit, a flash of blue magical light surged into Muzan's body.
Muzan, who had expected to be blown apart and was ready to split into 1,800 pieces to escape, found that the punches didn't hurt. But he couldn't move. An invisible, binding force was taking hold of his limbs. As Goku's fists blurred against his chest, the weight of the binding grew exponentially until it was an unbreakable shackle.
In his prime, Muzan might have broken through the magic. But in his current, depleted state, it was impossible.
"Alright, that should do it!"
Goku nodded, satisfied. He pulled out the oversized medical needle Tanjiro had given him and drew a large vial of blood from the frozen Demon King. Tanjiro had mentioned that the lady doctor needed the blood of the Kizuki and Muzan to find a cure for Nezuko. Since the Lower Moons were gone, this was the most important sample he could get.
As for his new move? It was a combination of his martial arts and the magic he had learned at Hogwarts. He realized that most offensive spells were "projectile-based" and easy for fast enemies to dodge. So, he fused them with his fists. By casting the spell at the exact moment of impact, he guaranteed a 100% hit rate.
He named this hybrid style: Fist-Magic!
"Okay. You've made too many demons and hurt too many people. It's time for you to go to the underworld and take your punishment."
Goku tucked the blood sample away and fell into the classic stance, his palms cupped at his side. He had heard enough stories from Mita and Kagaya to know that Muzan Kibutsuji didn't deserve a second chance.
"NOO!"
Muzan let out a final, pathetic howl of defiance, his plum-red eyes wide with the realization that his thousand-year reign was over.