The Tokyo sewers still held winter's chill in the early spring of 1991. Deep underground, where sunlight never reached, a strange black mud twisted and writhed. This wasn't ordinary mud—it was despair given physical form, born from sin and as empty as an abyss.
This thing—this "it"—twisted around in the darkness, gazing up at the sewer ceiling above. The black mud seemed to let out what could only be described as a resigned sigh. As it did, the dark sea of flesh spreading throughout the tunnel began to bubble and boil.
The black mud's name was Ryuuto. He wasn't always black mud. Originally, he was just a regular guy who'd somehow been transmigrated to this world. Trying to make the best of his bizarre situation, he'd scrambled to find work and eventually landed his first job. Unfortunately for him, that job happened to be in Tokyo's sewer system. Never in a million years would he have guessed that even after being reborn in a completely new world, he'd still end up stuck underground in the sewers, living what could only be described as a pretty underwhelming life.
But that wasn't even the worst part. On his very first day at work, Ryuuto, who had no clue about how tough life in Tokyo could be, was swallowed up by some mysterious black mud. He figured an early death would just mean getting reincarnated again sooner, right?
Except things didn't go as expected. After the black mud consumed his body, his soul somehow didn't get destroyed—it just kept fighting back. Maybe it was because his soul came from a higher dimension, or maybe there was just something about him that was weirdly compatible with the black mud. Whatever the reason, after six days and seven nights of this internal struggle, the mud's will finally surrendered to him. And once he took control, Ryuuto suddenly understood exactly what kind of creature he had become.
Throughout human history, this thing had gone by many terrifying names that scared billions of people: the Beast of 666, Sodom's Beast, Ten Crowns Beast, Antichrist, Anti-Messiah, Satan, and the Great Red Dragon.
It was basically sin and greed in physical form—the king of the world with the power to desecrate everything that is holy. Beast VI.
Even so, Ryuuto was still just a pupa that hadn't fully developed yet. The only way for him to grow the seven heads of sin and wear the ten crowns of blasphemy would be to gather seven heroic souls during the ritual known as the Holy Grail War.
"But I don't even want to destroy the world..." Ryuuto sighed to himself. He was so hungry. That was the worst part about becoming a Beast—feeling this endless hunger every single moment. He had completely lost track of time. Had it been a day? Three months? Ten years? Maybe even sixty-five million years? After his senses all started blurring together, even something as basic as keeping track of time became impossible.
Then one day, at some random moment, something changed. Nobody said "let there be light" or anything equally dramatic, but a ray of brightness suddenly appeared in the dark underground.
"Huh? That's weird... I thought I had set up a bounded field to keep people out."
An airy voice snapped Ryuuto back to awareness, and he lifted his faceless form to look up. Standing there was a girl giving off a soft glow in the dark tunnel. She was small, dressed in green, with pale blonde hair and light-blue eyes. Her doll-like face showed nothing but confusion. Like a beautiful flower somehow blooming in the filth, her name was Manaka Sajyou.
With knowledge from his previous life, plus memories buried in the Beast Core, Ryuuto suddenly understood everything. This girl was the one who had stolen a certain relic from the Holy Church and placed it underground in Tokyo to grow it as a Beast's egg. Manaka Sajyou—she was one of the people responsible for turning him from a human into a monster.
This girl, who looked more beautiful than any flower, glanced at his impossibly ugly form and somehow gave him a gentle look. "Good child, have you been behaving yourself down here?"
Her fairy-like voice echoed through the underground sewer. Despite not having any internal organs anymore, Ryuuto felt like his heart was beating wildly. The black mud's possessed will sent out one final ripple, and desires far beyond what any human mind could possibly handle came surging up from within the dark sea of flesh.
The Beast seemed to want to tell her something.
It wanted to feed.
It wanted to violate.
It wanted to destroy.
It wanted to kill.
It wanted to desecrate.
It wanted to bring about the end of everything.
But no, that wasn't quite right. Before all those impulses, there was one original desire that went beyond all worldly wants.
It wanted to be born.
Yes, that was it. "I want to be born."
And then, it made the very first sound that humans learn after birth—that universal sound that crosses all borders, races, and skin colors.
"Mama."
In the still air of the sewer, the black mud churned like a tsunami as it released its first cry.
"...How is this even possible?" When faced with this Beast that had somehow gained rational thought and language before it should have, Manaka was confused at first—but then she smiled. "There are still three years until the Fuyuki Holy Grail War. Are you really that impatient to be born?"
She smoothed her dress and crouched at the edge of the black mud. She rested her slender fingertips on her chin and tilted her head. "This is a problem. If you want to break out of your shell, you need to offer either the souls of seven heroic spirits or sacrifice thousands of human souls. Can't you just wait a little longer?"
Mama. Mama. Mama.
The black mud egg trembled.
Want to be born. Want to be born. WANT TO BE BORN.
The headless, hornless, faceless sea of flesh boiled and shrieked. Manaka responded by reaching her hand toward the darkness, her eyes full of love.
"Well, aren't you an impatient little thing," she said with a gentle smile.
But the moment her fingers touched the black mud, the girl's slender, fair fingertips started dissolving right before her eyes.
"What is this...?" Looking at her disappearing fingers and the crimson blood flowing out, Manaka's face didn't show even a hint of pain. Instead, she looked absolutely delighted, like someone who had just stumbled upon some amazing discovery.
"That's it," she whispered, speaking either to the creature or maybe just to herself. "As for a living sacrifice, isn't there one right here?" She gazed down at her dissolving hand with wonder.
"Mama, mama..." Ryuuto instantly understood what she was planning. He raised his body and let out another desperate shriek. He was trying to warn her to stay back, to not come any closer.
But she misunderstood his reaction, thinking he was just excited about being born soon. She knelt down and stretched out both arms. "Can't wait anymore, can you? Come on then, eat me. That's a good child."
With a smile on her face, the girl embraced the black mud.
"Oh..." She winced briefly, but then it was too late. The moment she touched the black mud, everything about her—her elegant clothes, fair skin, slender limbs, beautiful face—all of it started breaking down and decomposed without mercy.
Even Manaka, supposedly so powerful that people called her the "Root's princess," turned out to be just as fragile as a pile of salt when faced with the Beast.
Shortly after swallowing the girl, the boiling sea of flesh grew quiet again, as if nothing had happened.
One minute passed. Then another.
"Hmm, interesting," a boy's voice suddenly echoed from within the black mud. "Having a human body is somewhat limiting, but this feeling of having a solid form isn't so bad."
Just then, a white figure rose up from the black mud. No—there were actually two figures.
The newly-born boy stepped out of the black sea carrying Manaka in his arms. Ryuuto looked down at the girl cradled against him, who was now slowly opening her misty eyes.
The exhausted mother weakly raised her hand to touch the boy's face. "Ryuuto, let's go home."