"This is nothing but a useless blade that can't even kill," Sesshōmaru said flatly, his tone laced with faint irritation. In his eyes, even if his father hadn't left him Sō'unga, he should at least have inherited Tessaiga.
Yet instead, he had been given Tenseiga—a sword incapable of slaying demons.
What was that supposed to mean? Was he expected to abandon his pride as a warrior and live with mercy in his heart?
"It seems you still resent your father's decision," Satsuki said softly.
As she spoke, her gaze drifted toward the sword at Sesshōmaru's waist. With a faint pulse of gravitational control through her Tenseigan, the Tenseiga floated free from his belt and hovered before her.
Studying the celestial blade with her all-seeing eyes, Satsuki spoke calmly.
"Your father possessed both Sō'unga and Tessaiga—two swords capable of annihilating a hundred yōkai in a single swing. Yet despite that, he still chose to carry this—Tenseiga, a sword incapable of killing. Why do you think that is?"
"I don't understand."
To Sesshōmaru, the question itself was meaningless. In his view, Tenseiga could not even be compared to Tessaiga, much less Sō'unga.
"That's because Tenseiga serves as a gateway—a bridge connecting this world and the next. Its true power lies in its ability to cut down beings not of this realm. Conversely, it can also send beings of this world to the other side."
"A bridge between this world and the next?" Sesshōmaru asked, confused. "And how does that make it a weapon that complements my weaknesses?"
"When I guided you before, I awakened the power slumbering within you. I assume you've already used it. Did you notice anything unusual about it?" Satsuki's tone was calm and matter-of-fact. "Once you strike an opponent, they continue to suffer endless destruction. Such a power—do you truly believe it could exist without consequence?"
She smiled faintly. "If you swung that blade against the earth itself, would the continent not shatter?"
"..."
Sesshōmaru froze. Even he had sensed something unnatural about his ability, but had never been able to grasp what it was.
"That's why you must first understand the true nature of your Bakusaiga's power." Satsuki's hand traced lightly along Tenseiga's blade as she spoke. "Its surface effect appears to be unending destruction, but in truth, it's far more complex than that."
(For clarity: the power of Bakusaiga functions through a type of state-locking mechanism. Once a target is cut, the Bakusaiga's power locks onto the moment of injury and perpetually applies damage to that same state.)
In other words, while Sesshōmaru could continue to harm his opponents indefinitely, the intensity of that destruction was directly tied to his own yōki.
Sesshōmaru's yōki was formidable—especially after being enhanced by Satsuki's Tenseiga of Samsara Reincarnation. He had firmly attained the rank of a high-level daiyōkai.
Yet, as Satsuki had said, strength was always relative.
When Sesshōmaru faced Ryūkotsusei, now empowered by the Lunar Palace, his Bakusaiga's destructive power had proven insufficient.
Even his proudest technique, Sōryūha—the Azure Dragon Wave—had failed to destroy his foe outright. Simply put, Sesshōmaru's attacks lacked the necessary lethality.
Of course, had Ryūkotsusei not been strengthened by the Lunar Palace's influence, victory might still have been possible.
But Ryūkotsusei had long since reclaimed his true dragon form, his physical power vastly greater than before. Moreover, after completing his mission tied to the black magatama, he had been granted a fragment of power from the Great Brahma King.
The purple energy that had manifested on his body during the battle was, in fact, a weakened form of the Energy Control Authority—and it was this power that rendered Sesshōmaru's Bakusaiga useless.
Of course, Satsuki did not reveal these details to him. Instead, she went straight to the point.
"In essence, your technique simply lacks destructive power."
"If my strength is lacking, then why did my father leave me this Tenseiga—a sword that can't even kill—instead of the Tessaiga or Sō'unga that can unleash greater attacks?" Sesshōmaru asked, still unable to understand.
Satsuki sighed softly. She now realized that Sesshōmaru had entirely missed the meaning behind her words.
Seeing that Sesshōmaru still didn't understand, Satsuki switched to a more direct explanation.
"Tenseiga is not a weak or defective blade," she said evenly. "On the contrary, in terms of pure destructive capability, Tenseiga is actually the strongest of the three."
—Because Tenseiga possesses the attribute of Space. It is a divine sword capable of severing the boundary between worlds.
If one were to classify it according to the systems of the Fate universe, Tenseiga would be a specialized Anti-World Noble Phantasm.
What it truly cuts is not the physical body, but the fabric of space itself—and entities belonging to the otherworld. Its ability to resurrect the dead is merely a secondary effect, the result of cutting down the underworld spirits that bind souls beyond life.
The reason Tenseiga appears less impressive than Tessaiga or Sō'unga lies in one crucial limitation: it cannot alter the state of things within this world through a slash.
When Tessaiga cuts something, the target shatters—the strike directly changes the target's state.
Sesshōmaru's Bakusaiga, however, can complement Tenseiga's nature by locking onto the state of what it cuts.
By channeling that power through Tenseiga, Sesshōmaru can make the sword treat its target as part of space or as an otherworldly entity. Once something is recognized by Tenseiga as its specialized target, its destructive potential surpasses both Tessaiga and Sō'unga by far.
In the anime, when Sesshōmaru carried Tenseiga into the underworld to rescue Rin, the sword alone was able to purify nearly half of the Netherworld—proof enough of its overwhelming might.
"Tenseiga... the strongest of the three?"
Sesshōmaru looked doubtful, though Satsuki's confident tone left him momentarily uncertain.
He reached out and gripped the sword's hilt, drawing it swiftly. Spotting a butterfly fluttering nearby, he swung the blade toward it in one smooth motion.
As expected, the sword's light passed through harmlessly. The butterfly remained untouched, continuing to drift lazily through the air.
"Pfft..."
Ruri, who had just returned and caught the scene, nearly burst out laughing.
Sesshōmaru, however, stared at the spot where his blade had struck. For an instant—just a fleeting one—he felt something within that slash. But the sensation vanished too quickly for him to comprehend.
Satsuki didn't expect him to grasp the technique immediately. Even for her, merging powers as complex as Bakusaiga's with Tenseiga's essence would not be simple.
Yes—
The fusion of Perpetuity with Tenseiga's power.
Just moments ago, through her close contact with the sword, Satsuki had already recorded the unique force residing within the blade using her Status Record ability.
From the moment Satsuki first met the Great Dog General, she had noticed that the three swords he carried each radiated a unique power—energies that felt similar to Authority Laws.
At the time, relying on intuition alone, she had classified those three swords under the concepts of Slaughter, Protection, and Salvation.
But looking back now, that judgment had been too simplistic—so much so that she had nearly overlooked one of the most crucial underlying principles.
Waving her hand, Satsuki returned Tenseiga to Sesshōmaru, then turned her gaze to Ruri, who had just returned.
"Something to report?"
"Lord Satsuki, the task you assigned me is complete," Ruri replied respectfully.
"Oh? That was faster than I expected." Satsuki nodded slightly, then turned her attention to Sesshōmaru, who was still frowning down at Tenseiga.
"You and that sword will have plenty of time to grow accustomed to each other. For now, go and rest."
Sesshōmaru sheathed Tenseiga silently and walked toward his quarters within the Fushimi Inari Shrine.
Only after he had left did Kaguya finally speak. "What's the situation between him and the Lunar Palace?"
"If yōkai care about family ties, then they're sworn enemies—beyond reconciliation."
At that, Kaguya raised a curious brow. "And you? What's your relationship with him?"
"Mutual cooperation—or mutual exploitation," Satsuki answered without hesitation. "You can choose whichever phrasing you prefer."
"Is that all?"
"That's all."
Kaguya's expression fell slightly in disappointment. Apparently, curiosity and gossip were instincts shared by women of all species.
As for Satsuki, her sharp, no-nonsense reply left not even a sliver of space for speculation. Were she a man, one might call her the definition of a "steel-hearted straight arrow."
...
With Sesshōmaru's matter settled, Satsuki turned her attention to another—Hagorome Gitsune.
The Tail of Hagorome Gitsune had been obtained under her orders from the Great Brahma King, intended to empower Ruri—whose form was modeled after the Nine-Tailed Fox—with new abilities.
After all, Hagorome Gitsune and the Nine-Tailed Fox shared many similarities, and there was much to be learned from the comparison.
But first, she needed to receive and process the data that Ruri had deciphered from Hagorome Gitsune's power.
Through the mental network linking them, a luminous orb of data appeared within Satsuki's consciousness. A thread of light extended from it, transferring the decoded information directly into her mind.
For someone of Satsuki's intellect, absorbing the information was effortless. Within moments, the transfer was complete.
"I never would have guessed—Hagorome Gitsune was actually a close-combat fighter."
Satsuki opened her eyes slowly.
Though Hagorome Gitsune appeared to be a graceful and seductive woman, her combat style differed completely from the Nine-Tailed Fox of the Shinobi World.
While the Nine-Tails took the form of a massive fox, its essence was that of pure chakra—a vast, destructive energy being. Its combat preference leaned heavily toward unleashing raw power through its signature Tailed Beast Bombs.
That wasn't to say its physical might was weak. Any creature of such size naturally possessed monstrous physical strength. During the incident at the Uchiha compound, the Nine-Tails' rampage had nearly annihilated the clan outright. If not for Satsuki's Veil of Light and Shadow · Samsara Genesis, the Uchiha would have perished that night.
By contrast, Hagorome Gitsune was fundamentally a reincarnated yōkai. Her true form was far smaller and more delicate than the Nine-Tails' colossal body.
Though her yōki was no less potent, her centuries of integration into Kyoto's spiritual ecosystem had shaped her into one of the city's ruling forces. Consequently, her combat style was far more refined—less about overwhelming destruction, and more about precision.
She fought using her nine tails like blades—each strike measured, deliberate, and fatal.
If the Nine-Tails' power was vast and sweeping, then Hagorome Gitsune's was intricate and surgical.
But the greatest distinction lay in her most formidable ability—Reincarnation Possession.
That was what had captured Satsuki's interest most.
Because it represented the final missing piece in her development of Edo Tensei—the Reanimation Technique.
Infinite signal transmission and communication technology, combined with the massive Tenseigan as a medium, would allow her to perform remote soul control.
The Akasha Records, paired with Status Infusion, would provide the data needed to locate and restore the power of the deceased.
The secret of Goddess Kaguya's (Kaguyayo) undying soul ensured that even if her physical body were destroyed, her spirit would remain intact.
Tenseiga provided crucial data on how to open a passage between the underworld and the living realm.
And Hagorome Gitsune's Reincarnation Possession ability completed the final component—the mechanism by which a soul could inhabit a fresh vessel.
With that, Satsuki had fully perfected every element required for the creation of Edo Tensei.
It would not be long now before she could finally put her newly developed reincarnation technique into practice.
To that end, she dove her consciousness deep into the giant Tenseigan, setting aside even her ongoing work with the Yasakani no Magatama fusion project to devote herself entirely to the development of Edo Tensei.
...
Meanwhile, as Satsuki busied herself with this endeavor—far to the south of Japan's main islands, over the open sea—thick fog and ominous storm clouds cloaked the sky, blocking even the faintest glimmer of moonlight.
Thunder rumbled through the darkness, and flashes of violet lightning illuminated the roiling clouds. Hidden within that gloom, something massive and dreadful prowled—a presence vast enough to make the heavens tremble.
The stormfront rolled onward, an endless canopy of shadow stretching toward the coastline. Only then did the yōkai dwelling along the shore sense the overwhelming power approaching.
One by one, they lifted their heads—and then froze in terror.
Amid the clouds, framed by lightning and storm, a colossal demonic face flickered into view, so enormous it blotted out the sky for an instant.
Those with sharp enough eyes to glimpse it clearly didn't hesitate. Panic seized them. They fled in every direction, abandoning prey and companions alike, desperate only to escape the shadow that now loomed above.
"Hmph~ even after all this time, the yōkai of the mainland haven't improved one bit."
A deep, commanding voice thundered from within the clouds.
At its sound, the dark masses of vapor split apart, revealing the true form of the "demon face."
—It was a ship. A massive vessel suspended in the heavens.
Then another. And another. Two… three… no, thirty of them—each one a gigantic ghost ship drifting among the storm clouds.
At the forefront of this phantom fleet sailed the largest of them all—a colossal flagship as vast as an island. Upon its towering mast stood one of the Four Lords of the Realm.
Ōtakemaru of Mount Suzuka.
A smirk curved his lips as he gazed down at the fleeing yōkai below. Behind him, the enormous demonic visage adorning the ship's hull glowed ominously under the black moon. At his right hand, the Sanmyō Blade hummed softly, releasing waves of devastating sword energy.
"Humans, yōkai—it no longer matters. You need not search for that fabled land any longer," he declared coldly. "For Mount Suzuka... has come to you."
Raising one hand, Ōtakemaru gestured toward the heavens. One of the three divine swords within the Sanmyō Blade rose into the air and then came slicing downward with a thunderous cry.
A beam of sword light, vast enough to split the heavens, erupted from the ship—tearing through the clouds and cleaving straight toward the coast.
The energy wave cut across the entire shoreline, obliterating every yōkai caught in its path. With a deafening roar, it continued onward, carving deep into the land itself—splitting a mountain range tens of miles away clean in two.
The earth shook violently. One by one, the mountains along the coast began to crumble.
With a single swing of his blade, the shockwave swept across the entire region like a tempest, scattering the remnants of fallen yōkai into the howling storm.