Demon Slayer: Start With Heroic Spirit Legacy System

Approximately 400 years ago, the Tsugikuni family gave birth to two remarkable sons.

The elder, Tsugikuni Michikatsu, would later become Kokushibō, the first Upper Moon.

The younger, Tsugikuni Yoriichi, joined the Demon Slayer Corps after the tragic loss of his wife and child to demons.

Yoriichi, the creator of the Breathing Styles, revolutionized the Demon Slayer Corps by teaching these techniques, significantly elevating their strength and ushering in a new era.

If Muzan were given another chance, he would undoubtedly kill the demon responsible for slaughtering Yoriichi's wife and child.

"You're just dying to see me dead, aren't you?"

One day, while Muzan was traveling with Tamayo, he encountered Yoriichi Tsugikuni.

After arrogantly proclaiming, "I'm no longer interested in swordsmen who use breathing techniques," Muzan realized he might have made a grave mistake.

The moment Yoriichi saw Muzan, he understood one thing: he was born to defeat this man.

Opening the transparent world that he had mastered since birth, with his forehead demon slayer marked and wielding his bright red Nichirin Blade, Yoriichi instantly perfected the thirteenth form of Sun Breathing.

This technique seamlessly combined all twelve forms into one relentless sequence, resembling an unending, blazing sun, growing stronger and more invigorated the longer it lasted.

The result was inevitable: against Yoriichi, Muzan stood no chance.

As Muzan lay on the ground, torn into pieces, he could only hear Yoriichi's cold rebuke: "What do you take this world for?"

In desperation, Muzan exploded into 1,800 fragments of flesh, scattering in a desperate bid to escape.

In the ensuing chaos, Yoriichi managed to destroy 1,500 of the fragments. However, Muzan still managed to slip away.

It was during this battle that Tamayo finally broke free from Muzan's control.

This encounter left Muzan deeply scarred and paranoid, hiding away for years until after Yoriichi's death before resurfacing.

Now, someone has appeared with a striking resemblance to Yoriichi.

"He must be eliminated! He has to be destroyed before he grows stronger!"

The image of Zhou Yi's earth-shattering sword strike flashed through Muzan's mind.

"This is just a last-ditch effort on his part. I have six Upper Moon demons, and if necessary, I can create more! I will prevail!"

Muzan's face contorted with fury, and nearby, Nakime trembled as she timidly informed him, "My lord, they've arrived."

---

The first to enter the Infinity Castle was a beautiful woman.

With long black hair and large eyes, she was adorned with an array of ornate jewelry. Her heavy outer robe, a luxurious kimono typically worn only by the courtesans of Yoshiwara, hinted at her guise.

This was Daki, Upper Moon Six, who had been hiding in Yoshiwara as an oiran.

Her disheveled appearance reeked faintly of alcohol, her hurried arrival leaving no time to remove her makeup. As soon as she entered, she bowed respectfully to Muzan.

"She's quick," Muzan thought, nodding in approval before turning his attention away from her.

"Ah, Lord Muzan looks just as captivating in this female form!"

Daki, captivated by Muzan's elegance, only then noticed the battered and disheveled Dōma nearby.

"Lord Dōma? Who injured you so gravely?"

However, her concern brought Dōma no comfort. Instead, he felt a wave of embarrassment.

Should he admit that he had nearly been killed by a member of the Demon Slayer Corps?

He was, after all, Upper Moon Two! What would happen to his pride?

Without a word, Dōma's cold reaction silenced Daki, leaving her unsure how to respond.

Dōma and Daki had known each other for a long time. If Muzan's followers were likened to a malicious pyramid scheme, then Dōma was the one who had brought Daki into the fold.

It was Dōma who had transformed her into a demon and introduced her to Muzan, a crime of the highest order.

Just then, a finely crafted porcelain vase suddenly dropped from above, landing with a duang!

Though unscathed, the vase's abrupt appearance was met with indifference by the gathered demons.

From within the vase emerged a bizarre-looking demon, its entire body pale white, with yellow eyes and green lips.

Its lower half fused seamlessly with the porcelain, resembling the genie from a lamp. Sporting purple fins on its head, with eyes oddly placed on its forehead and mouth, it was further adorned with countless tiny hands.

This grotesque demon was Gyokko, Upper Moon Five.

Both Dōma and Daki stared at him with clear disdain.

"Hehehe, Lord Muzan, forgive my delay," Gyokko simpered, bowing deeply to Muzan before standing silently to the side.

Soon after, the rest of the Upper Moons began to arrive:

There was Hantengu, Upper Moon Four, a wrinkled old demon with horns protruding from his head, giving him a somewhat comical appearance.

Then there was Akaza, Upper Moon Three, who looked distinctly human. Dressed in a sleeveless training outfit, with short black hair, blue eyes, and pink eyelashes, his well-toned muscles were adorned with intricate tattoos.

In ancient times, there was a form of punishment called mo, where wounds were inflicted on a person, and dark ink was allowed to seep into the flesh, leaving permanent marks. The blue tattoos on Akaza's body were likely created in a similar manner.

As the Upper Moon Three, Akaza had a longstanding enmity with Dōma. Seeing Dōma in such a pitiful state, Akaza couldn't resist the opportunity to mock him.

"Well, Lord Dōma, which young lady managed to wound you this time?"

The source of their discord lay in their vastly different preferences. Dōma loved consuming beautiful young women, while Akaza, peculiar among demons, refused to eat women altogether. Their mutual disdain was palpable.

Dōma merely snorted and turned his head away, refusing to respond.

By now, almost all Upper Moons had assembled. Only Upper Moon One was missing.

Speak of the devil, and he shall appear.

"Apologies, Lord Muzan. I am late," a cold voice rang out.

From the shadows emerged a figure resembling a samurai. Dressed in purple, with a black katana at his side, and flame-like marks adorning his forehead and neck, he was the most fearsome of Muzan's subordinates—Kokushibō, the Upper Moon One. His most striking feature was his six eyes, the central row engraved with the characters for Upper Moon One.

A demon who could wield breathing techniques.

"It's fine. You're just in time," Muzan said, showing uncharacteristic leniency toward Kokushibō, even overlooking his tardiness.

"Let's begin." Muzan stood high above them, his expression unreadable.

The traces of Muzan's earlier rage were still evident. The gathered Upper Moons, powerful demons all, immediately recognized the remnants of his wrath and speculated about what had provoked him to such fury.

"It has been centuries since I last summoned all of you together. Centuries of complacency. I see that you have grown idle!" Muzan's voice deepened, and an oppressive aura radiated from him, silencing the demons.

"To think that such a formidable individual in the Demon Slayer Corps has emerged without any of you knowing!"

The Upper Moons, except for Dōma, now understood why Muzan was enraged.

Gyokko and Hantengu, ever loyal, were the first to step forward, their words dripping with obsequiousness. "Lord Muzan, allow us to handle this! We will dispose of this threat immediately!"

Though they were unaware of the individual Muzan referred to, their confidence as Upper Moons was unwavering. After all, for centuries, no Hashira who encountered an Upper Moon had ever survived.

Muzan cast them a cold glance. "You two? Hardly sufficient."

"Lord Muzan, entrust us with this task! Just tell us where to find this individual, and we will bring back his head without fail!"

Still, Muzan didn't grant immediate approval. Instead, he revealed shocking news that stunned all the assembled demons.

"Dōma was nearly killed by him."

The revelation struck like thunder. Even Kokushibō and Akaza, normally composed, were filled with fiery battle intent.

"What? Lord Dōma was defeated by a human?" As one of Dōma's juniors, Daki found this hard to accept. She covered her mouth in disbelief and looked toward the disheveled Dōma.

Dōma sighed and nodded helplessly. "That individual was cunning and wields the Flame Breathing technique to an extraordinary degree. The flames were too intense. I was caught off guard, and so…"

Dōma's explanation crafted the perfect excuse for his failure. It wasn't that he lacked strength—it was just that his opponent's abilities countered his own.

"Countered abilities, you see! It's not that I'm weak, but his tactics were unconventional!" Dōma didn't elaborate further, leaving it at that.

Hearing this, the other demons finally relaxed.

Oh, so it was just a counter in abilities. That explains it.

After all, Dōma's forte was his mastery of ice-based Blood Demon Arts. His close combat abilities were notoriously weak. Against someone with intense flames, it made sense for him to struggle.

But among the assembled demons, each possessed their unique strengths, and they all felt confident that such flames wouldn't be an issue for them.

Gyokko and Hantengu exchanged disdainful looks at Dōma before once again volunteering. "Lord Muzan, since the individual merely exploited a counter to Dōma's abilities, the two of us are more than capable of dealing with him!"

◇

After considering for a moment, Muzan finally agreed to their request.

"Remember, he has a high-damage technique. Once he uses it, he'll enter a state of exhaustion."

"You all should understand this."

"Yes, my lord!"

A powerful killing move naturally leaves one vulnerable afterward. As for how this conclusion was drawn?

Muzan himself experienced such drawbacks—how could a mere human child possibly surpass him? Impossible. Absolutely impossible!

Nakime strummed her biwa lightly, and Hantengu and Gyokko were promptly transported away. Muzan turned his attention back to the remaining Upper Moons:

"Dōma's subordinates seem to have found a lead on the Blue Spider Lily. Dōma, focus on this task."

"As soon as the information is confirmed, report it to me immediately!"

Dōma acknowledged the order and was also transported away by Nakime.

"As for the rest of you, find the headquarters of the Demon Slayer Corps quickly! Those rats hiding in the shadows have annoyed me for too long!"

Muzan's orders were brief, and the remaining Upper Moons swiftly received their assignments before being teleported away. Soon, only Muzan and Nakime remained in the Infinite Castle.

"I cannot tolerate you, even if you bear a mere resemblance in spirit!"

A flicker of ferocity appeared on Muzan's otherwise delicate face, quickly replaced by a hint of terror. The mere thought of that man's image brought him fear, and the old wounds on his body began to throb faintly.

"Yoriichi Tsugikuni!"

A furious roar echoed through the silent Infinite Castle.