In the past, someone from the Tohsaka family had attempted to improve upon this extremely costly and low-endurance magecraft, but as no particularly exceptional genius had ever emerged from their lineage, the effort had long since fallen into obscurity.
As a result, the Tohsaka family became highly conspicuous within the entire Fuyuki City—so much so that Kiritsugu Emiya had little trouble locating their stronghold.
However, based on his observations of the surrounding area, the magus Tokiomi Tohsaka appeared far more cautious than before.
"Northeast, 273.561 meters—three small avian familiars spotted on the fourth utility pole…"
"Northwest, 412.226 meters—on the balcony of Room 3, second floor of the apartment building, a bird's nest-type mimic familiar detected…"
"Due south, 557.586 meters—on the sign banner of a convenience store, a light-sensitive self-regulating familiar found…"
...
From the earpiece, the voice of his reliable assistant Maiya Hisau transmitted the information back.
Though her own magical ability was not particularly strong, she demonstrated extraordinary skill in manipulating low-grade familiars.
For that reason, most reconnaissance and scouting operations during their missions were handled by her.
In particular, the familiars she controlled did not rely on magical means for observation but instead used ultra-miniature CCD cameras—a highly effective method for evading magus detection.
Being well-versed in magecraft himself, Kiritsugu had a clear understanding of the capabilities of these familiars.
Since this mission required him to infiltrate and assassinate the target without being detected, he couldn't afford to dispose of any familiars along the way. Instead, relying on his knowledge of their patterns, he planned out a perfect infiltration route.
However, for a battle-hardened veteran like Kiritsugu Emiya, this was hardly a challenge.
His gaze darted rapidly between the buildings as he calculated the familiars' viewing angles, swiftly determining their blind spots.
Because many of these familiars were mobile, he couldn't linger in any one spot for long during the infiltration.
After committing thirty-four temporary stopping points to memory, Kiritsugu equipped his silenced pistol and tactical knife, then immediately set out.
He weaved through alleyways crowded with people, even diving into nearby trash bins without hesitation when necessary.
Should an unforeseen emergency arise, he could always activate his signature ability—Time Alter: Double Accel—to evade danger.
All in all, the operation didn't take long and faced little resistance.
After more than two hours of strategic maneuvering, he finally reached the front gates of the Tohsaka residence.
After all, this was the same professional killer who had once planted a bomb inside the Hyatt Hotel right under Kayneth's nose.
Breaking into the Tohsaka mansion was hardly beyond him.
The Western-style mansion stood tall among surrounding apartment blocks, its architecture somewhat old-fashioned.
Though many barriers and magical defenses surrounded it, none posed much difficulty for the well-prepared Kiritsugu.
Through infrared scanning, he detected a humanoid figure sitting at a desk inside what appeared to be a study, seemingly focused on something.
However, as he silently attempted to enter the mansion through a concealed chimney passage, the smooth infiltration suddenly changed.
Inside the chimney—originally meant for storing firewood—Kiritsugu spotted a gleaming cat's-eye gemstone halfway through his climb.
His heart froze instantly. A moment later, he sensed a surge of magical energy radiating from the stone's surface.
Judging from that surge, this was definitely not a friendly type of spell.
It was—a proximity-triggered explosive trap.
Reacting instantly, Kiritsugu invoked his signature technique once again.
"Time Alter: Double Accel!"
His black-clad figure blurred like a serpent of shadow. Perhaps thanks to his coat blending seamlessly into the chimney's dark interior, he vanished from sight as the gemstone's magical energy reached critical mass.
By the time the explosion was imminent, Kiritsugu had already reached the bottom and rolled out of the narrow space just in time.
However, that moment of escape confirmed one thing to him—his infiltration had been compromised.
The burst of magical energy from that cat's-eye gemstone was more than enough to alert Tokiomi Tohsaka to his presence.
This realization made Kiritsugu Emiya immediately draw his silenced pistol, but before he could act, a man's voice echoed through the room.
"Welcome, Kiritsugu Emiya. I've been expecting you."
Shock.
Kiritsugu turned his head slowly—and standing before him was not Tokiomi Tohsaka, the master of this residence, but another man wearing a faintly amused smile.
His body still bore traces of burn wounds, and in his hand he held a Black Key still stained with fresh blood.
The instant Kiritsugu saw him, he understood everything—he had walked straight into a trap.
"So it's you in this room instead of Tokiomi Tohsaka, huh?"
"Well, who's to say?"
Though he answered ambiguously, the look of pleasure on Kirei Kotomine's face only deepened.
The bloodied blade in his hand was still dripping, the crimson liquid yet to dry—proof that the victim's death had occurred only moments ago.
"You killed him… and intend to make me your scapegoat, is that it?"
"As expected of the Magus Killer… sharp as ever. I must apologize for taking action on my own initiative," Kirei said lightly.
Yet, no trace of remorse could be seen on his face.
"Still, I'm sure you understand why I did it."
"After all, it was easier for me to do it than for you—less risk, higher success rate. And isn't your creed that if sacrificing a few can benefit the many, then such sacrifice is justified?"
"When the one to be sacrificed happens to be yourself, surely you wouldn't have too many complaints either?"
Rather than being drawn into the man's twisted reasoning, Kiritsugu quickly analyzed the situation.
"So… are you planning to kill me here?"
"That is one option," Kirei replied calmly. "But not the best one. If you're willing to cooperate with me in fulfilling a joint commission from the Holy Church and the Mage's Association, then that alone will be enough to offset the crime of killing a magus."
"I don't care…"
"Of course you don't." Kirei flicked the blood from his Black Key before letting it dissipate into particles of light. "But what if this arrangement could help you realize your ideal of justice?"
As he spoke, Kirei tossed something toward him—a severed arm.
"This is all that remains of Tokiomi Tohsaka's body. You'd better make good use of the Command Seals still on it."
...
At the very moment Kirei Kotomine and Kiritsugu Emiya stormed Tokiomi's residence, several kilometers away, Satsuki's Tenseigan was observing the same scene in real time.
The perspective came from a familiar—the same one that had earlier delivered a message on Tokiomi's behalf.
For Satsuki, remotely controlling familiars was an effortless task.
As she watched the events unfold within the Tohsaka estate, she remained utterly expressionless—coldly observing everything without interference.
Thud~
She silently closed the magic tome in her hands, then unhurriedly picked up the next one. Her entire being was immersed in deciphering the very essence of this world's magical structure.
As for her Master, Iphis, she had long since lost the patience to read such incomprehensible texts.
Though Satsuki had granted her all of Irisviel's physical attributes and abilities, temperament and environment were things that could not be replicated.
After a long silence, a familiar, slightly lazy voice echoed once more within her mind.
"Long time no see, Host."
Although it had indeed been a while since she last heard that familiar, foolish tone, Satsuki still regarded the system's existence with a certain level of importance—after all, only through its power could she traverse time and space.
"Strictly speaking, it's been less than two weeks, so 'long time' might be an exaggeration."
Satsuki sank her consciousness deep into her mind, gazing at the golden sphere of light that represented the system—it seemed to have grown noticeably larger since last time.
"So, did you gain anything new during this period?"
"The database has been fully established, and this world has been successfully recorded. The analysis of its fundamental nature is nearing completion…"
The system rambled on with its usual incomprehensible jargon. Satsuki didn't interrupt it, but listened attentively, filtering for useful information.
Finally, the system's tone grew serious. "Upon completing the analysis of the Counter Force's true nature, would you like to receive the report?"
"Proceed."
"Understood."
The system began explaining the essence and operational principles of the Counter Force and Alaya.
In simple terms, the Counter Force was a safety mechanism born from the collective unconscious.
It was divided into two aspects:
The prayer of humanity—to avert destruction: Alaya.
The prayer of the planet—to prolong its lifespan: Gaia.
The birth of Gaia's consciousness was not surprising. Any planet that developed to a certain stage could potentially manifest its own will.
However, the existence of Alaya was far more peculiar. Why had such a consciousness emerged solely from human prayer, while other living beings lacked one?
The question flickered briefly through Satsuki's mind before she dismissed it.
It wasn't particularly important—no more significant than asking why a certain world possessed gravity, or why gravity measured 9.8 N/kg.
Ultimately, it all depended on who defined the rules.
The real question was this—why had the Counter Force targeted her specifically?
That led to another inquiry.
"What is the Counter Force's operational principle?"
"Based on the intelligence I've gathered and my study of this world's history," the system replied, "its operational logic isn't governed by strict standards. However, in simple terms: when an individual's actions threaten the survival of humanity as a whole, and humanity itself is powerless to stop them, the Counter Force manifests."
Upon hearing that, a spark of insight flashed across Satsuki's mind.
—In other words, if she could defeat the Counter Force's manifestation, then the entire pan-human history would be converted into a Lostbelt.
"As expected of you, Host—still as perceptive as ever…" The system paused briefly before adding, "And you, without question, have been classified by the Counter Force as an unstable element—one that threatens the survival of humanity."
"Wouldn't that have something to do with you, the so-called 'Strongest System Across All Worlds'?"
"Cough… ahem…" The system let out an awkward cough. "Well, during the dimensional transfer process, the energy loss was severe, so I had to 'collect' some of this world's resources to recover…"
"So the reason the Three Divine Kings' Sacred Wheel could persist as a Noble Phantasm even after world transfer—is also due to your ability, isn't it?"
"Hehe~ I merely did a little work behind the scenes."
Despite the humble words, the system's tone was unmistakably smug.
Satsuki rarely used the Three Divine Kings' Sacred Wheel, but she understood perfectly how powerful it was.
Though the system had never directly provided her with 'gift packs' or rewards, it had always offered her the most crucial assistance when it mattered most.
The Ōtsutsuki bloodline… the rapid adaptation to the immense power of the Tenseigan… the integration of the Demon Buddha form… and the Three Divine Kings' Sacred Wheel—
Each of these was a one-of-a-kind treasure of immeasurable value, and together they formed the foundation upon which Satsuki had risen to her current height.
Her wisdom and decisiveness were certainly her own, but these powers were indispensable.
Thus, Satsuki spoke sincerely: "Thank you."
"Eh? Host, that's… a bit unexpected. I'm not used to you being polite."
The system seemed momentarily flustered—it had long grown accustomed to her sharp tongue and queenly demeanor.
"Still, your sense of style could use some work," Satsuki added dryly. "Right now, you give off the impression of a nouveau riche."
Tsk~ The familiar sharp tongue had returned.
Yet, instead of sulking, the system seemed to have awakened some strange attribute. Rather than retreating, it happily circled around Satsuki, glowing with cheer.
"Ah, that's more like it! For a second there, I thought you'd been possessed by the Counter Force or something."
At first, Satsuki didn't react—but then, her gaze sharpened, and she looked seriously at the system.
"Possessed by the Counter Force?"
"Huh?"
The system froze, momentarily startled by her sudden change in demeanor. A question mark icon appeared over its golden spherical form.
"You just said—the Counter Force can possess people?"
"That's right," the system replied. "After all, to eliminate unstable factors that threaten this world, the Counter Force—being a collective unconscious—cannot manifest on its own. It can only act by possessing suitable mediums through which it can drive out threats to humanity's survival."
"Then," Satsuki continued coldly, "how strong are these individuals once possessed by the Counter Force?"
The system paused to think before answering, "Normally, the host only receives power sufficient to eliminate the designated unstable factor—no more. The Counter Force avoids granting excessive strength to prevent the medium from becoming a new threat."
Satsuki fell into deep thought.
Up until now, she had never revealed her full power in this world. So, how exactly did the Counter Force determine whether its chosen medium possessed enough strength to eliminate her?
If she were in its position, how would she act when faced with an overwhelmingly powerful enemy?
The answer came to her almost instantly.
"I see… I see. No wonder it felt so strange all this time."
As Satsuki's consciousness muttered softly to itself, the system wisely chose to stay silent—it knew better than to interrupt when she was thinking.
It was all a test.
Every encounter, every battle up to now—all of it had been a series of trials.
The opponents she had faced so far, while not weak, were still leagues below her in power.
This contradicted the system's earlier statement: "Normally, the host only receives power sufficient to eliminate the unstable factor—no more."
That could only mean one thing—these Heroic Spirits had merely been pawns, sent to gauge the extent of her abilities.
Once the Counter Force had gathered enough data through these test subjects, the true opponent—the real "finishing move"—would appear.
The one possessing power sufficient to eliminate the unstable factor.
"No wonder their strength has been increasing at such an absurd rate… That in itself is unnatural."
Satsuki withdrew her consciousness from the depths of her mind. In the outside world, the soft thump of a closing book echoed faintly.
"Iphis," she said calmly, "in the coming days, you'll likely become the next target for the other Masters in the Holy Grail War."
Without even turning around, Iphis replied nonchalantly, "I've been prepared for that ever since I joined the Holy Grail War. As long as we win, none of it matters."
"After all, in this world, strength is everything. Once you display enough power, changing their attitudes is only a matter of time."
Satsuki returned the book to the shelf and glanced at Iphis with quiet composure.
"Then you already understand," she said softly. "You know what you need to do."