Thunder Breathing

His lungs no longer drew powerful breaths, and his muscles no longer possessed the resilience a swordsman should have.

He had regressed from a Demon Slayer Corps swordsman into an ordinary person.

But demon blood had already entered his body. It belonged to Muzan, and an ordinary human body simply could not withstand such a forcible transformation.

One lump of flesh after another swelled beneath Kaigaku's skin, while his bones twisted and cracked.

His limbs rapidly expanded. His chest and abdomen ballooned like an overinflated ball, veins bulging one by one as his entire body deformed completely out of control.

"Save... save me..."

Kaigaku's voice abruptly cut off.

After his body expanded to its limit, it finally exploded into a mass of flesh and blood.

The instant the flesh burst apart, Kokushibo had already flashed more than a dozen steps away.

Scarlet chunks of flesh and blood splattered across the ground. Beside the corpses of several Demon Slayer Corps swordsmen lay an additional twisted heap of remains, distorted beyond recognition.

Kaigaku was dead, and he had died horribly.

All six of Kokushibo's eyes looked toward that mass of flesh. There was no pity on his face, only indifference.

"Trash."

He spoke softly.

He had been given Lord Muzan's blood, yet he did not even possess the qualifications to endure it.

Just moments ago, when Kaigaku had knelt on the ground and begged to live, he had sounded more certain than anyone.

"I can endure it! I definitely can!"

Yet less than a moment after the demon blood entered his body, he exploded.

Kokushibo had originally thought that this swordsman capable of using Thunder Breathing had some value worth cultivating.

Now, it seemed he was nothing special.

But soon, Kokushibo's gaze fell upon the scroll in his hand. He had heard Kaigaku's dying screams with perfect clarity.

"Where is my power?"

"My body... why..."

This was not simply a case of being unable to withstand demon blood. It was more like his cultivation and physical foundation had been drained away by something before the demon blood could transform him.

And this scroll had appeared far too conveniently.

The instant demon blood fell into Kaigaku's mouth, the scroll dropped from midair.

Kokushibo lowered his head and slowly unfurled the scroll. He could understand the words on it, but its contents were completely unfamiliar.

"Lightning Release: Lightning Ball Technique."

"Chakra."

"Hand seals."

Kokushibo read through it word by word, the scrutiny in his six eyes growing heavier.

Lightning?

This was different from Thunder Breathing.

Thunder Breathing merely strengthened the body through a special breathing technique, then used sword techniques to imitate lightning's speed and force.

But what was written in the scroll seemed to actually transform some kind of energy into lightning.

He had never heard the word chakra before.

Kokushibo raised one hand and tried to mobilize the power within his body according to the scroll's instructions.

There was no response.

He then clumsily shifted his fingers according to the diagrams.

Still, not a trace of lightning appeared.

The only things flowing within him were the power of demon blood and the swordsman's instincts honed through Moon Breathing.

So-called chakra did not exist for him.

Kokushibo stopped and rolled up the scroll again.

"Something from another world?"

He did not continue wasting time.

This thing had caused Kaigaku to undergo such a mutation when the demon blood entered his body. It was definitely not ordinary.

Just because he could not understand it did not mean Lord Muzan would be unable to see the problem.

Kokushibo tucked the scroll into his sleeve and gave the mass of flesh on the ground one final look.

"Kaigaku, you do not even have the qualifications to become a demon."

As his words fell, his figure flickered and vanished into the depths of the forest.

Fang Xu sat at the table and watched the entire exchange recording.

After the image faded, he did not speak for a long while.

Six eyes. Upper Rank One. Kokushibo.

And that youth kneeling on the ground, clutching his legs and begging for mercy—Kaigaku.

He recognized him.

"The Demon Slayer Corps world."

Fang Xu let out a breath, his expression somewhat strange.

Kaigaku had originally been Zenitsu's senior disciple. He had learned Thunder Breathing, yet he could only use forms other than the First Form.

Later, he betrayed the Demon Slayer Corps and joined Muzan. After becoming a demon, he even rose to an Upper Rank.

But this time, his fate had been changed directly by the exchange. The moment demon blood entered his mouth, he exploded first.

Fang Xu felt no psychological burden whatsoever. He even found it somewhat satisfying.

A scumbag who betrayed his master, caused his teacher's death, and looked down on Zenitsu deserved to die. The more miserable his death, the better.

"One Lightning Ball Technique scroll, and I got a future Upper Rank killed."

Fang Xu could not help laughing.

"This exchange was worth it."

Just then, a point of blue light suddenly appeared on the tabletop. It rapidly condensed into a thumb-sized crystal.

The crystal was deep blue throughout, with delicate lightning patterns moving within it like a bolt of lightning sealed inside.

The next instant, a notification appeared in Fang Xu's mind.

[Exchange complete.]

[Obtained: Thunder Breathing Crystal.]

[Notice: This crystal contains Kaigaku's Thunder Breathing training experience, swordsmanship experience, as well as part of the physique and cultivation he had developed through years of training.]

[Notice: Because the exchange extracted Kaigaku's cultivation and physique as a swordsman, his body could not withstand the demon blood transformation and ultimately collapsed.]

Fang Xu looked at the blue crystal, his breathing growing heavier.

So that was it. Kaigaku had not simply been unlucky. His Thunder Breathing cultivation and swordsman physique had been directly extracted by this exchange.

An ordinary person suddenly swallowing Muzan's demon blood—of course he would explode.

Fang Xu reached out and picked up the crystal. It was icy cold, yet a tingling electric current seemed to be hidden within.

The instructions were simple: consume it to absorb it.

Fang Xu did not hesitate. What he lacked most right now was something that could immediately complete his combat system.

Thunder Breathing suited him perfectly. The Rumble-Rumble Fruit wielded true lightning, and Lightning Release Chakra was also true lightning.

Thunder Breathing, meanwhile, used the human body, breathing, footwork, and sword techniques to imitate lightning. If the three could be combined, the improvement would definitely be substantial.

Fang Xu placed the crystal into his mouth.

The next second, the crystal rapidly melted.

A force both icy and scorching rushed down his throat and then exploded into his limbs and bones.

Fang Xu's body shook. His muscles, bones, lungs, and heart all seemed to be washed anew by a powerful force.

A vast amount of memories also surged into his mind.

The breathing rhythm of Thunder Breathing, the exertion of sword techniques, the variations in footwork.

Second Form: Rice Spirit, Third Form: Thunder Swarm, Fourth Form: Distant Thunder, Fifth Form: Heat Lightning, Sixth Form: Rumble and Flash.

And Kaigaku's countless experiences of swinging his sword, running, breathing, getting injured, and adjusting during training.

These things were not simply stuffed into his mind. They seemed to be carved directly into his body.

Fang Xu could feel that his breathing had changed.

Every breath drawn into his lungs could drive his muscles into action.

His legs felt as though they had been tempered thousands of times. Their explosive power, stability, and coordination had all surged dramatically.

Even the feeling of gripping a blade with his wrist was completely different from before.

If he had previously only been a novice led across the threshold of Kendo by Hatake Sakumo, then now he had suddenly gained the combat instincts of a mature swordsman.

Of course, that did not mean his Kendo had surpassed Hatake Sakumo's.

Thunder Breathing belonged to the Demon Slayer Corps system.

The Hatake Sword Technique belonged to Shinobi World swordsmanship.

The two were not the same thing.