Zouken Matou was a cautious man. Though he raised Sakura Matou, molding and controlling her from childhood, he considered her his most perfect creation, shaped by his will. Yet, he remained wary of her.
He trusted no one... not humans, not non-humans. Any being capable of independent thought, even a dog, was beyond his trust.
The only one he relied on was himself.
Thus, even though Sakura became a Master in this Holy Grail War, following his orders to monitor Shirou Emiya, Zouken prepared contingencies.
"With Crest Worms as the Matou family's magecraft, they possess unique and sinister properties, far more effective and elusive than other magecraft, especially for controlling others."
Zouken smiled, meticulously manipulating his most special Crest Worm, merging with it.
"Soon, I'll seize a young, powerful body. With it, I'll claim the Holy Grail and achieve eternal life!"
Zouken thought gleefully, chuckling aloud.
"Grandfather…"
A hesitant voice, tinged with fear, interrupted... his non-blood-related granddaughter. Hearing Sakura's voice, Zouken's delight grew.
"Truly unexpected, Sakura. You sensed my presence?"
Zouken spoke, his body writhing in this damp environment... not his aged flesh but his insect form, a Crest Worm.
"You studied magecraft under me and inherited the Matou Crest Worms. I taught you nearly everything I know, without reservation."
Sakura's voice wavered with doubt and fear. "Nearly?"
"Exactly, nearly. As expected of my dear granddaughter, catching the key detail. What I didn't teach you is how to use Crest Worms to carry a soul, a consciousness... my greatest secret. Among the Crest Worms I implanted in you is one bearing my consciousness.
"I'm surprised you sensed me, but sensing is useless. As we speak, don't you feel your consciousness fading, your body slipping from your control?
"It's inevitable. Soon, your body will be mine. I'll become Sakura Matou, and your soul will merely nourish these Crest Worms."
Zouken spoke with glee, using conversation to distract her, weakening her focus to accelerate the Crest Worms' work... a tactical move.
But soon, he sensed something amiss.
The environment felt strange. Though damp and blood-scented, it didn't feel like a human body!
The sensation of vessels and blood faded. Zouken realized he wasn't inside a body but a transparent container, facing an expressionless Sakura Matou!
Beside her stood her Servant, the masked Medusa, and another striking, mature woman, who eyed him curiously, asking Sakura, "This is your family's magecraft?"
"Crest Worms, used to perform magecraft... a unique form of Mystic Code," Sakura nodded, then asked, "Sister Medea, can I deal with him?"
"Have you made up your mind?"
A flicker of resolve crossed Sakura's face, then she nodded firmly. "Yes. When he tormented Kariya-san, I dreamed of this day. Years later, he's still as evil as ever. I have no attachments left. Ending him is best for everyone."
Zouken watched, stunned. He hadn't anticipated this. Worst of all, with his consciousness fully transferred here, his original body had collapsed... he couldn't return!
"You… you've been guarding against me?! No, that's impossible. I modified you early on... you couldn't have countered my magecraft so soon!" Zouken's insect form writhed, trying to gather mana to escape, but strangely, he couldn't break the fragile glass container. Human technology had trapped him!
"In truth, except for the first three days when the Crest Worms affected me, they've had no impact since. The deception was powerful, fooling the worms, you, Grandfather, Brother, and everyone else."
Sakura flashed a rare smile at Zouken.
"It's only natural. How could a magus of your level comprehend the magic of such a powerful magician? My body was healed by his power, but the magic circuits expanded by the Crest Worms were preserved... like reaping benefits without the cost."
"But your mana… without the Crest Worms, your usual mana…" Sakura's mana reserves were immense, terrifying even before the Holy Grail fragments. After their implantation, they were even more formidable. Deception could fake many things, but mana shouldn't be falsifiable!
"My mana was always vast. My body, transformed by Crest Worms, has high compatibility with their vitality... their mana. By keeping them barely alive, not letting them die, I convert their remaining vitality into my power. No issue there."
Sakura clapped her hands lightly.
The environment shifted. Massive nutrient tanks appeared, filled with countless Crest Worms!
The worms occasionally twitched their tendrils but mostly lay still.
They were in a coma... or suspended animation... instinctively converting vitality into mana, even siphoning it from their kin, all flowing into Sakura's body.
"I bred plenty of Crest Worms myself to keep you from noticing too many deaths. I couldn't replicate Matou-grade worms with mundane means, but creating ones with mana-conversion instincts was easy enough."
Sakura's lips curled smugly.
"Worms are easier to raise than people. With enough food, they multiply quickly. Mana resides in all life, Grandfather. Did I get that right?"
Zouken stared, speechless, his mind blank. He never imagined the girl he suppressed and controlled had achieved this.
The worst part wasn't her rebellion or cunning... it was that she'd deceived him since the third day in the worm pit, fooling him for over a decade!
No one noticed. Not until now, when his carelessness led him into her trap!
"A unique alchemical method. It's gruesome, but you're right... it's more efficient than killing. Even ignoring morality, worms outclass humans. You use magic circuits to extract mana, but vitality itself is mana. With a device to convert vitality, you can harvest fresh mana rapidly."
Medea shook her head. "My Master lacks such ingenuity. He stubbornly thinks using humans to refine mana is the fastest way."
Sakura smiled. "Many people I know work outside... some manage businesses or own companies. They taught me a principle: efficiency isn't just about unit output. You must consider many factors.
"Humans as mana sources are inefficient. Their unit yield may be high, but they're slow to cultivate, costly to acquire, and troublesome. Livestock, by contrast, is cheap, easy to obtain, and abundant. Their mana yield per unit is lower, but sheer numbers make up for it."
Sakura sighed. "Even ignoring morality for pure efficiency, some people can't see it and think they're clever."
"That's why I despise that man," Medea said. "He can't draw mana from the Greater Source due to his limited magecraft skill... a hurdle hard to overcome short-term. But failing to see more efficient, safer paths? That's just stupidity.
"And I loathe his obsession with harming children."
Zouken desperately gathered mana, unsure who they referred to. He guessed Medea's Master had met misfortune, and she now served another.
He didn't care. He just wanted to survive. If he could break this container, hide in a dark corner, and escape through sewers, he could rise again.
But he had no chance.
"You want me to do it?" Medea asked.
Sakura sighed. "Sorry, I'd rather not do it myself."
"No problem, I'll handle it." Medea raised her fingers. The next moment, the glass shattered, and an invisible mana hand seized the Crest Worm.
Zouken thrashed wildly, trying to break free, shouting, "You must want knowledge... how to gain a lasting body or extend life! Let me go, and I'll tell you everything!"
"I'm not staying here. I have business to return to the Throne of Heroes," Medea said. With a slight squeeze of her hand, the mana arm crushed Zouken's insect form, splattering viscous fluid across the floor.
A magus who schemed for centuries, the Matou ancestor, died without a tombstone or even an urn.
Flames flickered from Medea's fingertips, incinerating the spilled Crest Worm fluids, leaving only faint scorch marks.
Sakura stared at the shattered glass container for a long moment, saying nothing, then slowly left the room.
Moments later, her voice came from the doorway.
"Destroy those Crest Worms too. They're useless now."
Medusa, hearing the command, pressed a red button beneath the worm tanks.
Instantly, massive currents surged, killing the near-exhausted worms, converting them into raw mana that flowed into Sakura.
The machines self-destructed, crumbling into debris. Since learning magic from Morpheus and grasping more fundamentals, Sakura understood new mana applications. These Crest Worms were obsolete.
She'd kept them, thinking they'd serve a purpose. Now, she realized that purpose was fulfilled... showing Zouken his plan had failed from the start.
These now-worthless worms could be discarded.
"Your body is healthy, brimming with vitality, unlikely to fall ill unless you deliberately expose yourself to serious disease," Medea said, approaching Sakura, who had absorbed the worms' life force. "You might live beyond a century, nearing the human lifespan limit."
Such immense vitality promised a long life and a robust body!
This alone gave Sakura a significant edge in her future magical pursuits, surpassing most others!
***
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