Underworld, Maou Territory.
As the name implied, this was land that belonged to the Maou.
In the devil territories, near what could be called the center, there was a region that didn't belong to any noble house, nor was it the domain of any pureblood devil family. It was designated under the Maou's name—territory owned directly by the Maou.
Right now, high above Maou Territory, a sky-blue dragon cut through the night, flying toward a sprawling city.
"You settled those sisters in Luciferd?" Leo asked.
On the dragon's head, Leo and Ravel sat side by side, talking with the dragon beneath them.
"That's right," Tiamat's voice rumbled out from the sky dragon's mouth. "They're not monsters like me, and they're still young. Keeping them in the forest living a monotonous life would be cruel."
"So I arranged for them to live in an estate in Luciferd, where they can live like ordinary people."
Luciferd had once been the city where the old Maou Lucifer resided—the territory of the first-generation Maou, Lucifer.
It had once been the capital of the Underworld. But after the Old Maou Faction completely withdrew from ruling the devil world, the capital moved to Lilith. Luciferd became the former capital, no longer the center of everything.
Even so, as the old capital, Luciferd still held immense popularity throughout the Underworld under the name of a Maou city. The devil world didn't abandon it. They continued to develop it, and as a result, Luciferd had become a bustling metropolis second only to the new capital, Lilith. It housed numerous administrative institutions as well, drawing devils from all across the Underworld.
From time to time, the Maou and the upper echelons of the devil world would come here to work. Many large-scale events were also held in Luciferd, so its prosperity was in no way inferior to Lilith's.
Tiamat had deep ties with the devil world. Few knew where she truly stood, but as an ally acknowledged by the current Maou Beelzebub—and an underground referee for Rating Games—owning an estate in the old capital of Luciferd was effortless for her.
The thing was, Tiamat herself didn't like living in a lively city. She had always stayed deep within the Familiar Forest. If she hadn't been considering the twins' mental well-being, she never would've bothered setting up an estate in the suburbs.
Now, with Leo and Ravel along for the ride, she was heading for that estate in Luciferd.
"So what exactly are those sisters?" Ravel asked, unable to keep her curiosity in check. "Tiamat-sama?"
From the way Leo and Tiamat talked, the twins who might become their companions sounded… kind of insane.
Tiamat had even said they weren't human, weren't devils, and weren't even monsters…
Then what were they supposed to be?
Ravel wasn't the only one wondering. Leo had been curious too.
And at this point, Tiamat clearly wasn't planning to hide it anymore.
"Have you heard of the Oni?" Tiamat asked.
That made both Leo and Ravel freeze.
"The Oni?" Ravel said, surprised. "You mean the yokai from folklore—"
Yes. The "Oni" Tiamat referred to weren't ghosts or vengeful spirits or anything like that. They were a kind of yokai from folk belief.
They often appeared in Japanese folktales and local faith—usually depicted as stubborn giants with horns on their heads, red or blue skin, wielding iron clubs. Man-eating, hard-drinking, wild-haired, bare-chested monsters.
In this world, yokai existed just as truly as devils, angels, and fallen angels. And as one kind of yokai, the Oni were real as well.
But unlike the legends, the Oni of this world weren't wild-haired, blue-faced monsters with fangs. Most of them looked human—humanoid beings whose appearance matched humans.
They were born with terrifying physical strength. Even a three-year-old could swing a spiked club weighing over a hundred kilograms and go to war. They didn't eat people or drink themselves senseless, but most had violent temperaments. Especially once they became immersed in battle, glowing horns would sprout from their heads. When that happened, their power would multiply explosively, and their temperament would grow even more ferocious. They were a battle-loving race second only to dragons.
Historically, they had appeared many times. They enslaved humans, and like a night parade of a hundred demons, they brought calamity to the world alongside other yokai. That led to repeated clashes with humanity, and some were slain by powerful human heroes.
For example, the infamous Oni of Mount Oe—Shuten-douji and Ibaraki-douji—were said to have been killed by Raikou's Four Heavenly Kings. That story was famous even in human folklore.
So the Oni were an incredibly powerful warrior race. They didn't quite reach the terror of dragons, widely regarded as the strongest race, but among yokai, they were still one of the top-tier strongest species. In terms of raw combat power, even Nekomata who could wield Senjutsu fell short.
But…
"Weren't the Oni wiped out?" Ravel asked quietly.
Leo dug through his own memories, recalling something he'd once read.
Supposedly, because the Oni were so battle-crazed, their population dwindled over time. By the modern era, they had become vanishingly rare, with only one or two scattered villages still hiding in the world.
Then ten years ago, what was believed to be the Oni's last refuge was destroyed by a group of rogue cultists. Every Oni in the village was slaughtered. Not a single survivor.
Because of that, most people believed the Oni had gone extinct back then.
Tiamat's voice reached their ears.
"The Oni truly were on the brink of extinction. But ten years ago, I happened to pass by that Oni village after the massacre. I rescued two children who fought until the very end from those rogue cultists."
At that point, how could Leo and Ravel not understand?
"So the sisters you're giving Leo-sama…" Ravel's eyes lit up. "They're the Oni children you saved?"
Oni survivors.
That was an absurdly valuable find.
The Oni were born with bodies stronger than almost anyone—second only to dragons if you only looked at physical strength. And once their horns were awakened, a casual strike could split mountains and shatter stone. They were the perfect frontline fighters.
Even Oni who weren't adults yet could contend with a High-Class Devil the moment their horns awakened. Adult Oni, even without awakening, were barely inferior to a High-Class Devil—and once awakened, they were said to be unstoppable. That was the kind of reputation that built.
Now that the Oni were nearly extinct, those two sisters might be the last survivors. If Leo could bring them under his banner, it would be a massive boost to the growth of the Eligos servants.
"As long as your master can actually reincarnate them," Tiamat said flatly, pouring cold water on the excitement. "To be honest, even among the Oni, those two are extremely special."
"Because they're twins, they were each born carrying only a single horn. They're extraordinarily rare one-horned Oni."
"Horns are the Oni's source of power, and Oni pride themselves on having two. So twins born with only one horn each are often treated as trash and disposed of. They almost never survive."
"But those sisters survived—and during the annihilation ten years ago, they fought to the end despite being children."
That alone was enough to show how abnormal those sisters were.
And what Tiamat said next only confirmed it.
"The older sister is exceptionally gifted—a child prodigy that only appears once in a century, hailed as the Reincarnation of the Oni God. Before she was even ten, she was already the strongest among her people, praised and expected by her parents and clan."
"The younger sister's talent is far inferior to her sister's. But she has a trait—once her horn awakens, she enters a complete berserk state and her power skyrockets. In that state, even among the Oni, only her sister could stop her. The clan feared her."
"That's why they were called 'the One-Horned Oni God.' Either one of them carries terrifying power within."
"The One-Horned Oni God…"
Just that title alone said everything about how dangerous and special they were.
"No wonder so many devils couldn't reincarnate them…" Ravel muttered under her breath.
Just hearing it like this, she could already tell how hard it would be.
If it were only one, a single Mutation Piece would probably solve it. But they had to take both sisters together—making it unimaginably difficult.
"To be honest, if you weren't a special existence yourself, I wouldn't be optimistic either," Tiamat said.
"Because of that mutated trait of yours, your Evil Pieces all carry the traits of a Mutation Piece, don't they?"
If so, then Leo might be the only person capable of meeting the sisters' reincarnation requirements.
"I hope you succeed," Tiamat said, her voice quieter now. "That way, those sisters can finally have a place to belong."
As she spoke, she began to descend.
Ahead of them, a prosperous city came into view.
Luciferd, outskirts.
In a relatively remote rural area stood a luxurious estate.
It was a strangely mysterious place. Supposedly no one knew who owned it. Only two maids were ever seen leaving, occasionally heading into the city to shop. Other than that, no one came or went, and the conspicuous estate had sparked countless rumors.
Some said an ancient devil lived there, and if you earned his recognition, you'd inherit his legacy and rise to prominence in the devil world.
Some said a hidden treasure was stored inside—enough wealth to buy an entire city.
Some said a terrifying monster was sealed within, and if anyone broke in recklessly, the seal might be undone and disaster would befall the Underworld.
Others claimed a powerful weapon slept there, and whoever obtained it could dominate the entire Underworld and become a Maou.
Because of those rumors, plenty of devils had tried to sneak in over the years. In the end, they were either thrown out by the two maids… or they simply vanished, never emerging from the estate again.
Over time, the estate became a forbidden place—coveted and feared in equal measure. No one around here dared to trespass.
But today, someone came.
"We're here," Tiamat said.
She had already taken human form, landing from the sky with Leo and Ravel before the estate's front gate.
Click…
Almost at the same time, the doors swung open, and two figures slowly stepped out.
They were a pair of girls who looked exactly alike—same face, same height, nearly identical build, like they'd been carved from the same mold.
They wore matching outfits: maid uniforms based in black, exposing slender shoulders, paired with short skirts that traced their curves in a way that felt almost… provocative.
Both wore white headpieces. With their identical faces, someone who didn't know better might've thought there was a mirror between them reflecting the same person.
Of course, there were differences.
The girl on the left had large pink eyes and a short pink bob. Her bangs covered her left eye. She was slimmer, her figure less pronounced.
The girl on the right had large blue eyes and a short blue bob. Her bangs covered her right eye. She was the same height and similar in frame, but noticeably fuller than her sister.
Anyone could tell they were twins.
They seemed to have sensed Tiamat's arrival. As they came out to greet them, they bowed respectfully—like proper maids.
"Welcome back, Tiamat-sama."
"Welcome back, Tiamat-sama."
Even their voices were nearly identical. Their movements were precise and perfectly in sync—nothing like the image of battle-hungry Oni.
"I'm back, Ram, Rem," Tiamat said.
Some of the coldness in her presence seemed to melt when she looked at the twins. She gave them a small nod.
Behind Tiamat, Ravel studied the sisters with focused interest.
Leo, meanwhile, narrowed his eyes, a quiet realization settling in.
"So it really is them…"
After hearing Tiamat's description, he'd already suspected these might be people he knew.
And sure enough.
"These are the Oni's last descendants," Tiamat said to Leo. "The one on the left is the older sister, Ram. The one on the right is the younger sister, Rem."
Then her gaze sharpened.
"From here on out, it's up to you."
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You can read up to chapter 193 on patreon.com/NiaXD.