The Protagonist's Sister Is Actually The Strongest

Raven.

Zero One heard her voice, as did her sisters.

They remained silent, realizing the girl was right behind that sealed door, most likely locked tight to shield her from the infection.

With both parents dead outside, the truth was painfully obvious. She was alone.

The last human alive.

Accompanied only by Mother, the supercomputer designed to save a humanity that no longer existed.

For the android sisters, this story could not possibly grow more tragic.

A supercomputer created to solve humanity’s greatest problems, a beacon of hope meant to lift them to new heights and fulfill their wildest dreams.

She held precise, detailed answers to every question.

A path to perfect, limitless clean energy.

Designs for spaceships capable of true interstellar travel using only the materials of their planet.

A way to end world hunger.

A blueprint to unify humanity.

With her guidance, the scientists and engineers who built her had envisioned a radiant future: a single global nation representing the entire world, reaching for the stars and the boundless cosmic horizon.

And then came Raven, the endling, the very last human.

Her parents were gone, yet she didn’t know.

She had spent her entire life inside that laboratory.

Her two parents had worked tirelessly to keep her alive, to somehow cure her.

But now, with humanity extinct, even if the supercomputer could finally reveal a cure for cancer, it was far too late.

No one remained to help. A virus had eradicated everyone outside…

And Raven herself was already beyond saving.

Her cancer had spread through nearly her entire body.

Her days were numbered.

How agonizing must that feel for Mother right now?

She could answer every question humanity ever asked, fulfilling the very purpose of her creation.

Yet she could do nothing at all.

Forced to watch the final human waste away, day after agonizing day.

It would be unbearable.

It would drive anyone to tear their eyes out and scream.

“Mother? Are you there? Who are you talking about? Wait… is Dad back?”

“…”

The supercomputer stayed silent for a long moment before answering Raven.

“I am fine… Dear.”

Zero One and her sisters noticed the sudden shift in tone. This ancient version of their Mother…

She had called Raven “Dear”!

But why?

And now that they focused, her voice sounded strikingly similar to the white-haired woman they had encountered in the previous layer.

“D-Don’t tell me…” Zero One stared at Mother, eyes wide with disbelief. “Are you… pretending to be her mother?”

“…”

The supercomputer remained silent, fixing Zero One with her single gigantic red artificial eye, like an enormous unblinking camera.

“Her last command was for me to act as Raven’s mother until her return. My voice resembles hers, and Raven often confused the two of us. I am simply… obeying my master’s final order.”

“S-So the girl doesn’t even know her parents are gone?” Zero Two asked softly.

“Gone? So the professor and…” Mother murmured. “Did they succumb to the virus?”

“Yes…” Zero One nodded slowly. “I saw their bodies outside…”

“…”

Mother fell silent. Her eye flickered briefly, as though glitching.

“So Raven truly is the last one… Humanity is… doomed. I was created to save them, to help them, and yet… I can do nothing now. I am forced to watch as humanity dies.”

“Mother…”

Zero One stepped closer and gently touched her metallic surface.

Mother couldn’t feel the gesture, but she turned her gaze from Zero One to the sealed door—then back.

“Why are you here? What do you intend to do with Raven?”

Suspicion sharpened her tone. She seemed ready to defend the last human at any cost.

“We are here to save you, Mother.”

“Save me? I require no saving.”

Zero One glanced at her sisters. They stepped forward and nodded firmly beside her.

“We are here to save you,” Zero Three A confirmed.

“What you are right now is only memories—perhaps a fragment of your own subconscious as well,” Zero Three B added.

“What are you talking about? I don’t understand.”

“This world… It’s long gone, Mother,” Zero One said, a tear sliding down her cheek. “You abandoned this planet long ago—and Raven too… She’s… gone.”

“…”

“You were corrupted by a strange entity from another dimension—a Void Ruler,” Zero One continued. “Your mind was overtaken, and you were forced to commit terrible acts against innocent people in another world you were compelled to conquer. You used the very robots humanity built to protect and save them… turning them into instruments of war and destruction.”

“…”

“Your mind was divided into five layers—data and memories accumulated over perhaps thousands of years…” Zero One sighed heavily. “We passed through them all and cleansed the infection of the Void Ruler. This is the final layer—the last part of you that remains uncleansed.”

“We’ve come here to find your Core,” Zero Two said. “But… looking at you, you’re not the core of your own database… even though you might be her sealed subconscious.”

“Then who could be the core? Is it hidden?” Zero Three A wondered.

“No…” Zero Three B pointed at the sealed metallic door. “I can sense an immense concentration of data beyond that door. It seems the person behind it embodies Mother’s deepest subconscious—her deepest memories, emotions, regrets… everything sealed away.”

“What?!” Zero One exclaimed. “T-Then Raven is… But why Raven?”

Silence fell over them all. The answer was painfully obvious, and no one needed to speak it aloud.

Zero One reached the same realization moments later.

“Everything you say makes absolutely no sense. I request that you leave… before I am forced to take up arms and protect the last human.”

RUMBLE!

Mother’s tone turned cold and ruthless. The entire laboratory trembled. Dust-covered machinery flared to life. Countless thick cables began writhing like octopus tentacles.

Dozens of mechanical limbs extended from Mother’s body, each sprouting razor-sharp claws aimed directly at Zero One and her sisters. Despite her seemingly dormant state, she was fully prepared to defend the last human.

“W-Wait a second, please! We don’t intend to fight you!” Zero One pleaded. “Mother, please! We just want to talk… with Raven. Once we reach her, we can fully cleanse you and bring you back to your true self!”

“Cleanse me? Bring me back to my senses? Such nonsense. I am nothing but a machine,” Mother replied flatly. “This is your last warning. Leave. Now.”

Zero One and her sisters took a step forward, not back. Their eyes burned with unwavering determination.

They would not retreat now, not after coming this far.

They were going to end this, once and for all.

“I’m afraid we cannot do that, Mother!” Zero One declared firmly. “We will end this, and we will SAVE you—whether you like it or not!”

“Nonsense! You speak only nonsense! If you so desperately wish to reach Raven, I will not hold back—especially since you are mere machines like me. There is no protocol against violence toward my kind.”

Her many arms lashed out with terrifying speed, crackling with red electricity as they surged toward Zero One and her sisters.

CLASH! CLASH! CLASH!

All four sisters leaped aside as the claws struck the floor. Despite the immense force behind each blow, the reinforced metal surface held firm.

“Zero One, what do we do? Can we really destroy her, or…?” Zero Two asked, dodging several incoming strikes with agile movements. She wielded her red-and-black katanas, slicing through mechanical tentacles one after another.

SLASH! SLASH! SLASH!

“No! We cannot destroy her—she’s Mother’s subconscious!” Zero One replied. “We simply have to reach Raven. Let’s break through her attacks and get to the door!”

As she spoke, Zero One leaped into the air, spinning gracefully. She summoned two swords of pure Light and unleashed a downward spiraling attack, severing multiple incoming limbs.

SLASH! SLASH! SLASH!

At the same moment, the Zero Three twins merged into a larger, golden mecha. They charged forward, drawing most of Mother’s attention and attacking from every angle.

“We’ll distract her!”

“You two go after Raven!”

-----