A small terraced house in Archway, in the suburbs of London.
The perfect, boring sanctuary that Alisha Gray had spent three years building fell in exactly five minutes.
"...It's cramped. And the ceiling is low."
"If you're going to complain, break off those pointlessly magnificent horns before you come in."
Alisha coldly rejected Dantalion, the giant Demon Duke who had to duck to enter the living room.
When a large man over 190 centimeters tall stands in a room lined with small furniture meant for humans, the space feels oppressive just from that.
On top of that, the faint residue of magic he emitted (which could easily make an ordinary person faint) made the air in the room tremble and crackle.
However, he was not the true threat.
"Woooow! A TV! This is a box called a TV, right?! There are tiny people inside, aren't there!"
"Hey, Puck! You can't touch that, Papa will get mad!"
"Hmph! There is no throne fit for me to sit on! There are nothing but shabby chairs!"
"Excuse me, old lady over there. The pattern on this cushion is fatally tacky. My eyes are going to rot."
Screech, screech, stomp, stomp.
The moment they took off their shoes, the four toddlers scattered around the living room and began to run wild like a storm.
The boy innocently smacking the TV screen (Puck).
The girl trying to stop him, only to nearly knock over a vase instead (Riri).
The spiky-haired boy crossing his arms and acting bossy (Miko).
And the slightly mature girl accurately tearing into Alisha's interior design sense (Yumi).
A vein popped with a twitch on Alisha's temple.
"...Sit down."
The tone of her voice was low.
However, she mixed in just a tiny fraction of the high-purity intimidation she possessed as the Former Ultimate Military Force of the Royal Magic Association.
Freeze.
Perhaps sensing an instinctive terror, the four children stiffened like snakes glaring at a frog, and obediently scrambled up onto the chairs of the four-seater dining table.
"Miss Gray, I apologize... They are usually more... no, they are always like this, but..."
"Save the excuses for later. Sit. You too."
Alisha used her chin to prompt the ruler of the Demon Realm, who was flustered and trying to line up excuses, and forced him to sit on a small stool meant for children.
The sight of the giant demon sitting hugging his knees was terribly comical, and carried an air of sorrow.
Alisha headed to the kitchen and took out some cheap cereal she had stocked up on from the back of the cupboard.
It was colorful, coated in plenty of sugar, exactly the kind of cereal children love.
She poured it roughly into four bowls, added milk, and slammed them down on the table with a thud.
"Breakfast. Eat."
Pushed toward them with spoons, the children peered into the bowls curiously.
"What is this colorful gravel? Are you telling me to eat this?!"
Miko stood up and pointed at the bowl with a short finger in protest.
"If you don't like it, you don't have to eat. Just starve to death."
When Alisha stated this coldly, Miko flinched with an "Ugh," and timidly brought a spoonful of red cereal to his mouth.
"...Mmm. It's crunchy and sweet. Not bad. To satisfy my palate, this gravel is no ordinary thing!"
He fell easily. Miko began frantically shoveling the cereal into his mouth.
"Nom, nom... sweet... yummy..."
Puck wasn't using his spoon, but had his face shoved directly into the bowl like a dog, eating away.
Dantalion hurriedly tried to teach him, "Puck, use your spoon. It's bad manners," but Puck wasn't listening at all.
"I'll help pour the milk!"
Riri stood up energetically and tried to snatch the milk carton from Alisha's hands.
"Ah, wai—"
Splash.
Her aim was spectacularly off, and the milk formed a white puddle on the table.
"Awawawa, I'm sorry! Riri is a good girl, but! I messed up!"
Riri was on the verge of tears.
Alisha took out a dishcloth without a word and wiped up the milk with a sigh.
"...So? If I eat this lump of sugar, will my skin get all rough and dry like yours?"
Yumi was the only one who hadn't touched the cereal, and while staring intently at Alisha's makeup-free face, threw words as sharp as blades.
"...You're getting the green pepper punishment later."
"Eek."
Yumi obediently gripped her spoon.
While the four of them were engrossed in their cereal (in both a physical and mental sense), Alisha crossed her arms and stared straight at the Demon Duke in front of her.
"Now then. For the time being, we have an environment where we can talk quietly. We haven't done introductions yet. You said your name is Dantalion."
"A-Ah. I am one of the 72 Pillars of the Demon Realm—"
"I don't need your titles. So, what about these four little monsters?"
When Alisha asked, the children who were chewing their cereal looked up one after another.
"Me?! I am Miko! The strongest boss who rules the sandbox and the jungle gym! Someday I will make all the toys in the world mine!"
With milk all around his mouth, Miko puffed out his chest.
"I'm Puck! Puck likes sparkly things! Your eyes are sparkly, Miss, they look yummy!"
Puck said something terrifying with an innocent smile.
He was pure and innocent, but gave off a dangerous scent of acting purely on instinct.
"I'm Riri! My job is to take care of Papa and everyone! I'll help you lots and loooots too, Miss!"
The very person who spilled the milk puffed out her chest proudly.
She gave off a strong vibe of being a troublemaker driven 100% by good intentions.
"...Yumi. For now, I'll put up with it until this house gets a slightly more decent design. Nice to meet you, tacky old lady."
Yumi, talking back until the very end.
"...I see. All of their memories are gone."
Alisha massaged her temples to fight off a headache.
"That's right," Dantalion opened his heavy mouth. "During the accident in my laboratory, they were subjected to a regression curse. Not just their physical bodies, but their mental age and memories have regressed to that of humans around seven to ten years old."
"Is there a way to return them to normal?"
"...I do not know. According to my calculations, to construct the spell to break the curse and gather the necessary materials, it will take several years at the earliest."
Several years.
Hearing those words, Alisha's vision went completely dark.
Several years?
With these noisy children and a demon on the verge of death from overwork, for several years?
"Why don't you just raise them in Hell? You're a Duke, aren't you? You must have a castle or something."
"Impossible." Dantalion shook his head. "The Demon Realm is a world where the strong eat the weak, where power is everything. Currently, my political enemy, Duke Malphas, is aiming for my downfall. If he learns that they, my direct subordinates, are in such a powerless state... they will be assassinated. Without a doubt."
Dantalion looked at Alisha with pleading eyes.
Deep within those amber eyes, there was no demonic cunning, but simply a pure, heartbreaking wish to protect his family.
"Miss Gray. No, Alisha. With your power, and the strong concealment barrier placed upon this house, you can hide them from both the eyes of the Demon Realm and the Magic Association of the human world. Of course, I won't ask you to do it for free. Money, magic power, anything, I will pay it."
Alisha let out a deep, long sigh.
There was no escape route anymore.
If she abandoned him, these children would be killed, or at best, turned into experimental animals by the Magic Association.
She had once been completely exhausted from being needed and had thrown everything away, but... she wasn't cold-hearted enough to kick away children pleading for help right in front of her.
"...Fine. Let's form a temporary Nanny contract."
At Alisha's words, Dantalion's face lit up brilliantly.
"R-Really!? You have my gratitude, Lady Alisha! I shall immediately prepare the contract—"
The moment Dantalion tried to pull out a parchment scroll wreathed in ominous black flames from the empty air.
Alisha lightly snapped her fingers.
With a small pop! sound, the parchment instantly burned up and turned to ash.
"Ahhh!? The blood contract of my house!"
"Don't open up dangerous things like that in my living room. We do the contract by my rules."
Alisha brought a 100-yen notepad she bought at the supermarket and a ballpoint pen from the kitchen counter.
Then, she spread it out on the table.
"There are four conditions.
First. You will pay a massive compensation to cover the children's living expenses, child-rearing costs, and the trouble you are causing me. The currency will be Pounds, or exchangeable precious metals.
Second. You may have work in the Demon Realm, but while you are in the human world, you will participate in raising them with everything you have as a 'father.' I will not allow you to leave everything to me.
Third. This is my house. You will absolutely obey my rules.
Fourth. This is the most important. You must absolutely, absolutely never let my true identity be discovered by the Magic Association. If you neglect hiding your magic power even slightly, I will kick you outside that very instant."
As Alisha stated this while tapping the notepad with the tip of the ballpoint pen, Dantalion gulped and nodded deeply.
"Understood. We shall do everything exactly as you say."
"Good. Then, sign here."
On the notepad Alisha held out, Dantalion signed Dantalion with a trembling hand.
It was the moment a Child-Rearing Pact, heavier than a blood contract, was formed between a Demon Duke and the former strongest mage.
"Miiiisss! Seconds of cereal!"
"Me too! I should be able to pour the milk better this time!"
"Only gather the red gravel and put it in my bowl!"
"...Hey, isn't this milk right on the edge of its expiration date?"
No sooner had the signing finished than noisy, squawking voices echoed from behind.
"...My quiet retirement."
Alisha muttered in a voice mixed with despair, looking like she was about to crush the ballpoint pen in her grip.
Dantalion awkwardly looked away, simply sipping the cheap black tea Alisha had brewed with single-minded focus.
Thus, the quiet terraced house in Archway transformed into the noisiest and most dangerous daycare center, situated in the space between the Demon Realm and the human world.