This is a hopeless, tragic world, where no future can be glimpsed.
In 2020, the terrifying virus originally called the "Devil Virus," also known as the Gastrea Virus, suddenly broke out. Those infected rapidly mutated into ferocious monsters known as Gastrea. In 2021, humanity was utterly defeated in the war against these creatures, the flame of civilization flickering on the verge of extinction.
Gastrea carry within them the Gastrea Virus—a virus capable of rewriting life itself. It analyzes the host's genetic traits, twisting and redesigning them into the most survivable (and most grotesque) forms. Its speed at rewriting DNA defies natural law, a cheating speed incomparable to any known lifeform on Earth.
The Gastrea Virus corrodes human cells at a terrifying pace. When the corrosion rate exceeds fifty percent, the host loses all semblance of humanity, transforming completely into Gastrea. During this process, some individuals even manifest original abilities previously impossible for humans.
Human civilization nearly collapsed under the assault of these horrifying creatures. Gastrea possess immense regenerative abilities and aggression; almost all infected cells can rapidly regenerate, rebuilding telomeres with unnatural speed. The sole known substance capable of suppressing their regeneration and weakening their cellular activity is a rare metal called Varanium, whose emitted magnetic field disrupts Gastrea biology.
During the war against the Gastrea, humanity made countless sacrifices as territory after territory fell. After their decisive defeat, mankind's territory drastically shrank. Humans were forced to construct massive rectangular black walls—1618 kilometers tall and about 1 kilometer wide—made entirely from Varanium around their remaining settlements. These gigantic structures, known as "Monoliths," resembled gravestones of civilization, monuments mourning humanity's past yet also serving as their fragile, final defense against death.
Like the Eldians in Attack on Titan who erected high walls to protect themselves, humanity in this world built walls as well. However, the Eldians' walls were meant to protect those outside, while humans here only sought to shield themselves from the Gastrea.
This false peace lasted for ten full years.
When Nursery Rhyme arrived in this world, she felt as though the sky itself were about to collapse.
She loathed this world's atmosphere—it was saturated with cold, viscous malice, permeating every inch of air. The darkness of humanity was omnipresent here, as omnipresent as oxygen. Between every breath, she could smell despair, betrayal, and cruelty, nearly suffocating her.
Few anime series displayed human malice as blatantly as Black Bullet, placing it openly and starkly before its viewers.
Just upon arriving, she had already witnessed two policemen pointing their guns at a small, helpless girl who'd given up resisting, prepared to blow her head apart.
"Cursed Children"… this referred to girls born to mothers infected by the Gastrea Virus orally during pregnancy. The toxin accumulated in the fetus, and these girls were born already infected, retaining human appearance and sanity, but also bearing Gastrea's trademark red eyes and various special abilities.
Incidentally, "Cursed Children" were always girls. In human biology, all embryos begin female during the first seven weeks before differentiating gender, some becoming male later. For reasons unknown, the Gastrea Virus interfered with the factor determining gender, preventing embryos from ever becoming male.
In Nursery Rhyme's eyes, humanity in this world had long been terminally ill. Perhaps they should have gone extinct a long time ago, yet by some fluke, they survived that catastrophe—like a creature surviving a calamity meant to kill it. They no longer had the right to choose life or death, only clinging feebly to existence as their condition steadily worsened.
Nearly everyone who survived that disaster ten years ago was fundamentally broken. Unable to find meaning in life, yet unwilling to die, they wandered like hollow shells, walking corpses.
Newborn children, immersed in this malicious atmosphere for prolonged periods, would gradually become just as broken as their predecessors—not merely numb and indifferent, but actively joining the swamp of cruelty.
Nursery Rhyme believed she had arrived in this world precisely to do something.
Not to protect the world, nor to rescue humanity, nor even to pursue justice—but rather, to help these pitiful "Cursed Children" experience sweetness akin to candy.
After all, she was Nursery Rhyme, who existed solely to fulfill her vow to "make children smile"—a true "hero to children." But in this particular world, she had no intention of playing the savior or humanity's protector; she wished only to be the hero for these children.
...
The location was Russia, within a forest near Moscow.
Ten years earlier, humanity had abandoned vast territories. Additionally, the Gastrea Virus accelerated plant growth; now, former cities and idyllic countryside had been consumed by twisted forests and monstrous vegetation. These areas became forbidden death zones humans dared not enter. Massive trees and creeping vines flourished unchecked atop the ruins, creating dark labyrinths filled with viral spores and unknown threats.
On an abandoned building sprawled a Gastrea of massive proportions, as large as a small hill. It suddenly opened its enormous maw, unleashing an eardrum-splitting roar. Superficially resembling a giant enraged bear, it was covered in glossy black armor plates like a scorpion's shell and bore a thick, muscular tail. Poisonous saliva dripped continuously from its fangs, a foul stench rendering it nearly impossible to approach.
"Hello! Would you like to play with Nursery Rhyme?"
Nursery Rhyme innocently approached this bear-shaped Gastrea, greeting it warmly, but received only a hostile roar in response. Seeing the creature about to pounce, Nursery Rhyme pursed her small lips, troubled.
"Hmm… Can't call Exploding-Neck Dragon again; he'd frighten others. Who should I invite this time…? Ah! Got it!"
Having made her decision, Nursery Rhyme showed a brilliant smile, cupped her hands around her mouth in the shape of an adorable little trumpet, and loudly called out:
"Help me, Mr. SpongeBob!"
Nursery Rhyme's call still echoed in the air when a vivid yellow figure appeared instantly by her side, accompanied by a comical "pop!" It was a square sponge with limbs and a bright, beaming smile. Overflowing with seemingly inexhaustible energy, he excitedly brandished the spatula in his hand, eagerly eyeing the Gastrea nearby.
"I'm ready! I'm ready! I'm ready!"
With his iconic, enthusiastic shout repeated three times, he instantly became a yellow whirlwind, charging straight toward the bear-scorpion hybrid monster. His spatula flashed through the air, moving so swiftly only afterimages remained. In the blink of an eye, the terrifying Gastrea had been neatly reduced into a pile of… perfectly sliced meat patties?
This wasn't the end. That overly energetic sponge somehow pulled out a full grilling setup from who‑knows‑where and began cooking patties with expert ease. The sizzle of frying meat spread through the forest along with a mouthwatering aroma. In smooth, practiced motions he stacked patties with buns, lettuce, tomato, pickles, sauerkraut, onions, cheese—then squeezed ketchup and mustard into a cheerful smiley face on top.
In the blink of an eye, right there in the depths of the forest, a small mountain made entirely of hamburgers had risen from the ground.
After finishing everything, the yellow sponge took an exaggerated, massive breath—his stomach area inflating into a ball from all the air. The next second, his mouth literally transformed into a bright yellow megaphone. His voice, amplified severalfold by this bizarre organ, made nearby branches and leaves tremble violently.
"OOOOOOOOOH—SQUID—WARD—! Three hundred and sixty‑five Krabby Patties filled with all my love are complete! Each one carries a full year of blessings just for you—!!"
The soundwaves were nearly enough to flip the broken ruins around them. After shouting, he suddenly froze, scratching his hole‑filled head as realization dawned.
"Oh—barnacles! I almost forgot. I'm not at the Krusty Krab right now… and Squidward isn't here either…"
"Look! Krabby Patties. Wanna eat? These are super popular back in Bikini Bottom."
Nursery Rhyme held out a Krabby Patty with a bright, innocent smile and walked toward the two little girls.
The pair looked extremely similar—likely twin sisters. Both of them had red eyes like Gastrea. But when they saw the burger in Nursery Rhyme's hands, identical expressions of disgust flickered in their crimson gaze.
"This… was probably made from Gastrea meat, right?"
"Is it even safe to eat?"
Having witnessed firsthand how that yellow sponge had processed that disgusting Gastrea, their doubts were… understandable.
"It's edible! No matter what kind of creature it comes from, Mister SpongeBob can always turn it into a Krabby Patty…" Nursery Rhyme reassured them with a smile. But after a moment of thought, she put the patty away.
"But… that Gastrea was kinda ugly, so looking at it might mess with your appetite. And this place isn't really fit for eating either… But Master says good kids must never waste food, and we mustn't waste the hard work of the farmers. Nursery Rhyme wants to be Master's good child, so… so… so…"
She puffed up with determination.
"…So I'll just let the Jabberwocks eat the burgers!"
The twins opened their mouths, wanting to gently point out that Krabby Patties made from Gastrea probably didn't have much to do with any farmer's hard‑earned harvest—but before they could speak, Nursery Rhyme had already summoned several Jabberwocks. The overwhelming pressure radiating from the creatures shut the sisters up instantly.
Before meeting this bear‑type Gastrea, the twins and Nursery Rhyme had encountered another Gastrea. The twins had only begun to warn her that Gastrea could only be killed with Varanium before they saw a gigantic monster appear beside Nursery Rhyme—larger than the Gastrea itself—and slap the creature into a cloud of blood mist with a single claw.
All stats EX—pure, overwhelming numbers! Built on sweat and effort!
The Jabberwock was a monster that appeared in Alice in Wonderland.
"Jabberwock is my friend. If we're in danger, it'll show up to protect us. It's a little shy, but I'm sure you'll be good friends in no time."
When Nursery Rhyme happily introduced the Jabberwock with those words, the twins could only stare with a field of question marks floating above their heads.
It? Shy?
It had casually swatted a Gastrea into nothingness.
And she was saying it's shy?
If that is "shy," then sorry—they were terrified. Terrified of being the ones flattened next.
Because the Jabberwock scared them half to death, Nursery Rhyme refrained from summoning it this time. But honestly, the singing, dancing yellow sponge had provided them with an entirely different kind of horror.
At least the sponge was gone now—vanished because Nursery Rhyme complained he was too loud. The sponge's mouth had never closed once, and it could even turn the holes on its body into second and third mouths, chatting with itself. Truly strange. Truly indescribable.
This pair of sisters was brought out of the Moscow region by Nursery Rhyme. In Russia, the status of "Cursed Children" was even worse than in Tokyo. The Gastrea that attacked this region was the "Plague King," and order here had collapsed far more completely.
"It's the sea!"
After two days of travel, Nursery Rhyme and the twins finally emerged from the forest. Before them stretched an endless, glittering blue ocean, gleaming under sunlight, the sound of waves rolling forward like a song.
Because they were "Cursed Children," the twins hadn't complained of exhaustion even after traveling for two days. After all, physical fatigue was nothing compared to the bone‑deep pain of being viewed as monsters by the world.
Nursery Rhyme spread out her arms in excitement, as though she wanted to embrace the entire sea breeze. She took a step forward to cheer—and then suddenly stopped, puzzled, turning to look at the twins who still stood awkwardly in place.
"Why aren't you shouting with me?" she asked, tilting her head, eyes full of confusion.
"Uh…" The older sister's cheeks reddened slightly. She muttered, embarrassed, "It's too childish… How can we do something like that?"
"How is it childish?" Nursery Rhyme put her hands on her hips and glared indignantly. "Maybe it's childish for adults, but for us it's perfect! Kids should act like kids! Come on! Again! This time both of you shout with me!"
Unable to resist the sparkling, expectant look in Nursery Rhyme's eyes, the twins finally surrendered. Clumsily, they extended their hands and tightly held Nursery Rhyme's. The three stood shoulder to shoulder on the shoreline, inhaling a deep, salty breath of ocean air.
"THE SEA——!!!"
Three young voices, full of strength, overlapped and sailed out across the wind.
Pulled along by Nursery Rhyme, the twins couldn't help smiling too. For a moment, they felt like birds breaking free of a cage—their bodies so light they might take flight.
On the beach, there were several other figures—almost all adorable girls with red eyes, all of them "Cursed Children."
They gathered in small clusters of two or three. And in each cluster, there was a Nursery Rhyme.
These girls were all Cursed Children whom Nursery Rhyme had brought out of Russia.
Some people, upon seeing so many Nursery Rhymes gathered on the beach—identical in appearance, expression, smile—fell briefly into shock and confusion. But after recalling the miraculous, impossible acts Nursery Rhyme had shown during the journey, they eventually decided that this scene wasn't much to be surprised about at all.