Chapter 1: How to Be a Good Parent (Step One: Don't Kill the Baby)
To say the Demon King's palace was intimidating would be an understatement. It was a ten-story gothic nightmare with lava moats, spiked towers, and a permanent thundercloud mood setting. Basically, it looked like Halloween had thrown up on a medieval castle and added WiFi.
Inside the obsidian throne room, the Demon King himself was lounging like a bored rockstar in a beanbag throne made of skulls. His black cape trailed across the floor, and his giant horns had tiny bells on the ends for no apparent reason. He wasn't even paying attention to his advisors—nope. His eyes were glued to a handheld game console.
If you imagined Satan as a lazy Twitch streamer who played Mario Kart while planning the apocalypse, you'd be close.
"Tomorrow," he announced between gaming grunts, "I will destroy all humans."
The room fell silent. Even the lava bubbling in the ornamental death fountains seemed confused.
"You know what?" he added, pausing the game to flick imaginary lint from his crimson robe. "Don't you guys find humans super annoying? They're like... everywhere. And all their talking and wars and TikToks? Totally grosses me out. Killing them all would be, like, super refreshing."
He grinned and unpaused his game. "Think of it as a cleanse. For the world. Like a spa day, but with global annihilation."
The demon advisors—gray-skinned, horned, slightly terrified—whispered among themselves. Finally, one of them, a frazzled elder demon named Balgon, cleared his throat.
"But, Great Demon King," Balgon said nervously, "tomorrow is Lord Meiryuu's wedding ceremony."
The Demon King paused his game again. "Seriously? That's tomorrow?"
"Yes, Your Malevolence."
He groaned. "Ugh, fine. Then I'll destroy humanity the day after."
A different advisor flipped through a flaming planner. "Uh... that day's the Great Chupacabra Hunt in the Land of Darkness."
"What? No way, that's this week?!"
"Yes, sire. You're the guest of honor."
"Man, I am way too busy for global destruction," he muttered, slumping deeper into his throne. "Ugh, being evil is exhausting."
There was a long pause.
Then, with all the grace of someone throwing out a soda can, the Demon King said, "Whatever. I'll just have my son do it."
The advisors blinked.
"Your... son, my lord?"
"Yeah, he was born, like, yesterday or something. Right, Hilda?"
A tall, silver-haired demon maid appeared from the shadows like a very punctual ghost. She bowed crisply.
"Yes, my king. Your son is strong, healthy, and already destroyed three nurses by accident. His cry summoned a minor earthquake."
"See?" The Demon King beamed. "Perfect little planet smasher. Hilda, take my boy to the human world. Drop him off with some rando. Let him grow up there and, you know, eventually destroy the place."
"As you command."
"Oh, and make sure he eats his greens and terrorizes his classmates. Like, a healthy mix."
And that was how Beelzebub IV, future destroyer of Earth, got packed in a magic satchel, launched into the human world like an evil Moses.
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Once upon a time—because all ridiculous stories start that way—there lived a young man named Tatsumi Oga.
Now, you've probably heard stories about kind-hearted heroes. Maybe they rescue kittens or help old ladies cross the street. Well, Oga was sort of like that. Emphasis on sort of. He was kind-hearted, if your definition of "kind" included punching people so hard they forgot math.
Oga was cool, handsome, ridiculously strong, and the kind of guy your parents warned you not to make eye contact with. He was so popular that even the teachers at Ishiyama High (aka the school for future criminals) tried not to give him homework.
And despite looking like he wrestled wild boars for breakfast, Oga was respected. Not feared. Respected. Though, to be fair, mostly out of fear.
Which brings us to today.
Oga stood proudly over a small pile of moaning delinquents, his school jacket flapping in the wind like a victorious superhero cape—if superheroes solved problems by suplexing people into the concrete.
"Everyone, bow down to me!" Oga declared, arms crossed, like a monarch surveying his broken, twitching kingdom.
The leader of the gang he'd just pulverized was trying to speak through a cracked lip and what may have once been a pair of sunglasses.
"M-Man… we're really sorry we got outta hand there," the leader wheezed. "You see, you're the legendary Invincible Oga of Ishi High and, well... you were just lying there in the schoolyard like a peaceful panda napping in the sun. It was too tempting!"
"No," Oga replied flatly, pointing to the shattered wooden bat lying nearby. "That wasn't your 'chance.' That was 'attempted murder.' If I wasn't me, you'd be explaining to the cops why there's a body in the clubroom."
There was an awkward pause.
"...Yeah," the leader admitted sheepishly, "We were kinda hoping you'd die."
Oga gave them a look like a disappointed big brother—if your big brother was a demon-fighting muscle machine.
"Well," he sighed, "let's go wash off your shame."
Cut to the next scene, where Oga, in his usual delinquent-chic attire, was at the riverbank. The wind whistled through the reeds. The birds chirped. A single delinquent was being held upside down by the ankles.
"I really hope these bloodstains come out," Oga muttered, dunking the gang leader into the river like a mop. "You guys got your stupid on all over my jacket."
"Blub-blub–I'm–sorry–blub!" the leader sputtered.
The other delinquents were just watching silently, weighing whether to run or applaud.
Then it happened.
Something came drifting down the river. At first it looked like a log.
Then the log snorted.
"W-Wait… is that a dude?!" one of the delinquents yelled, eyes going wide.
Sure enough, floating toward them like a retired sumo wrestler on vacation was an enormous old man. Long beard, horned helmet, and some kind of magical baby carrier strapped to his chest.
Every single delinquent screamed and scattered like roaches.
Except Oga.
Because of course he didn't run.
"Oh great," he muttered, as the old man bobbed closer. "What now? A drowned Santa?"
With exactly zero panic and 100% frustration, Oga waded in and grabbed the massive old guy by the scruff of his shirt, hauling him out of the water like he was fishing a vending machine out of the river.
He set him down and stared. The old man coughed, groaned…
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Dragging a giant river-man to shore was not how Tatsumi Oga had planned to spend his day. He thought maybe a nap. Some rice crackers. Possibly punch a vending machine if it ate his change. But no. Instead, he was soaked, annoyed, and now staring at an unconscious old guy who looked like a Final Boss from a discount RPG.
Oga plopped the guy onto the riverbank.
Then the man... split in half.
Literally.
Like a zipper had opened up his back and out came—
"A baby?" Oga blinked.
There, sitting peacefully between the steaming halves of the now-vanished old man, was the cutest baby he had ever seen. Big green eyes. Tiny horns. Floating sparkles like it had just won a magical baby pageant. Its diaper had actual embroidery. Oga had questions.
"Huh," he said, scratching the back of his neck. "What a cute—wait. Nope. This sucks."
He stood over the baby like a mechanic inspecting a cursed engine.
"What do we do now?" he muttered.
The options played in his brain like a broken playlist:
Fight it?
Run away?
Threaten it?
Make it cry?
Kill it?
Oga paused. "Hold up. Killing is bad. Yeah. Bad. That's a parenting red flag."
He took a deep breath. "Okay. Breathe, Oga. You're an adult. You're sixteen and your emotional range is the size of a matchbox, but technically you're an adult."
He crouched down, trying his best to be gentle.
"Hey, uh... boy?" he said, face still set in his usual expression: the look of someone about to ask if you valued your kneecaps. "You lost?"
The baby stared.
Zero reaction. No giggle. No fear. Just pure, calm judgment. Like it was already questioning his life decisions.
"Hm... something's off," Oga murmured. "Maybe I gotta try... that thing normal people do."
He imagined it in his head—smiling, waving like a French kindergarten teacher.
"Hi! You lost, sport? S'il vous plaît? Want some juice?"
He even mentally pictured giving a thumbs-up and saying "buddy" like a sitcom dad.
Then he looked down at his actual face.
"…My face."
He touched it.
His reflection in the river looked like a mid-tier yakuza boss who hadn't slept in three days.
"Yeah, okay. That's not the look. One sec."
Oga turned around and covered his face with his hands, like rebooting his system.
"Just need... a little facial recalibration," he muttered.
He spun back around and gave it a try.
"Like this? Come here. That's a good boy," he said through gritted teeth, forcing what could only be described as a horrible grimace of friendship. His eyes twitched. His mouth twitched. The baby's soul twitched.
Silence.
Then—
The baby giggled.
Oga blinked. "Huh?"
The baby crawled forward and attached itself to his leg like a magnet. Sparkles and demonic aura mixed together like a kawaii death fog.
"Wha—No. No way," Oga protested, backing up as the baby latched onto his chest. "My demon face?! That's what you like?!"
He looked down in disbelief.
The baby snuggled into him. Little sparks of red lightning zapped in and out of the air. A magical mark glowed faintly on Oga's shoulder. Birds flew away. Somewhere in the distance, a monk fainted.
"…Well. Crap."
And just like that, Tatsumi Oga—a teenage delinquent who could bench press a motorcycle—was now a full-time dad.
To a demon baby.
Who thought his scariest face was adorable.
This... was going to be weird.
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Oga did not know how to hold a baby.
You'd think it would be simple—one arm under the butt, one around the back, keep the soft spot safe, etc.—but no. He carried the baby the same way you'd carry a duffel bag full of grenades: cautiously and with the constant fear something might explode.
The baby, for its part, didn't seem to care. It just clung to Oga's shirt like a koala glued on with affection and demonic duct tape.
And so, with the baby still latched to his chest like an extremely judgmental bib, Oga stomped his way to the back alley behind Ishi High where his two closest friends were waiting.
"Guys," he said in his usual blunt tone, "I have a situation."
Enter Takayuki Furuichi, resident girl-chaser, disaster magnet, and the walking embodiment of "not built for this."
Furuichi blinked. "Oga… is that a baby?"
"Yes."
"A real baby?"
"Still yes."
Furuichi's face paled like he'd just seen the tuition bill for parenting.
"Okay. Okay. Not panicking," he said, visibly panicking. "We can explain this. We can fix this. There's a fire station like three blocks from here. You just leave it at the door like a normal person and walk away—"
"Furuichi."
"Was there a body? Just blink twice if someone died. Or like... exploded. This is very 'someone exploded' energy."
"No one exploded," Oga said flatly. "A big old dude floated down the river, split in half like a melon, and left the baby with me."
Furuichi stared.
"You kidnapped a baby from a magical watermelon man?!"
"I didn't kidnap anyone!" Oga snapped. "He gave me the baby! Voluntarily! And then vanished into sparkles or steam or some creepy demon gas, I dunno!"
"I'm going to jail just for being your friend," Furuichi muttered.
Meanwhile, standing quietly nearby, was Yuji Itadori—the sunshine boy of the group, human golden retriever, and future king of "I can fix this."
Yuji leaned forward and looked at the baby with a smile. "Wow, he's super cute! What's his name?"
"I dunno," Oga admitted. "He hasn't said anything. Doesn't cry. Doesn't eat. Just kinda... stares into my soul like a miniature grim reaper."
Yuji waved at the baby. "Hey little guy! You okay there?"
The baby gave no response. No giggle. No smile. Just clung to Oga like he was life support.
Yuji nodded thoughtfully. "He definitely likes you, though."
"Yeah," Oga sighed. "Unfortunately."
Furuichi, still holding his head like it was about to fall off, stepped back in. "Okay. Step one: where did you even find him again?"
"River."
"Of course it was a river. Nothing normal comes out of rivers in this town!"
"And step two," Oga continued, ignoring the spiral of chaos behind him, "he doesn't eat. We tried milk. Rice. Baby snacks. Guy just looked at it like I offered him a tax form."
"Dude," Yuji said, lifting the baby's tiny hand and shaking it gently, "are you secretly a cursed object?"
The baby blinked.
Then proceeded to chew on Yuji's finger with surprising strength.
"Ow! He's got some bite!"
Oga folded his arms. "Told you. Demon teeth."
Furuichi, now half-resigned and half-mad, sighed loudly. "So... we're keeping the baby?"
"No," Oga said.
"Yes," Yuji said at the same time.
"Ugh," Furuichi groaned. "You guys have the combined IQ of a rice cooker. Do you even know what babies need? Diapers! Vaccinations! Love! You can't just beat up street punks and call it parenting!"
The baby giggled.
Everyone froze.
"…Wait," Yuji said slowly, "he laughed at that?"
Oga turned to face the baby. He made his demon-face again—eyebrows furrowed, sharp glare, the whole "I will break your soul" expression.
The baby clapped.
"Oh no," Yuji whispered. "He likes your evil face."
"I told you!" Oga said. "He gets weirdly affectionate whenever I look like I'm about to throw someone into orbit!"
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Just when the trio thought the day couldn't get any weirder, a gothic umbrella floated down from the sky.
Like, literally.
One minute they were arguing about baby formula and emotional damage, and the next—BOOM—a blonde woman in a frilly black dress and parasol cratered into the pavement like some Victorian meteorite. She landed with enough poise to make a ballerina jealous and enough menace to make a horror movie rethink its villain.
Furuichi let out a very undignified squeak.
"Okay, is that—an angel? No, a demon? A supermodel? What anime did she fall out of?!"
Oga squinted. "...A flying French doll?"
She raised one eyebrow and tilted her parasol. "Heh. You seem to be extremely mistaken, sewer man."
"...What."
"There is no way," she continued, her voice sharp and confident, "that the young master would get attached to you."
There was a long pause.
"...Who the hell are you calling sewer man?!" Oga snapped, clearly offended on several levels. "And where did you even float in from, you flying ditz?! You got the nerve to come down here and boss us around at my school?"
Yuji blinked, still processing the situation. "Wait, did she say 'young master'? Is that—like—an actual title or just a weird nickname?"
"Why isn't she even flinching?" Furuichi whispered, sweating bullets. "She just called Oga 'sewer man' and didn't explode. She's tough."
The mysterious umbrella lady ignored them completely and walked right up to the baby still clinging to Oga's chest.
"Come, Young Master," she said sweetly, extending her arms. "Hilda has come to take you back."
The baby stared at her.
Then tightened his grip on Oga like he was clinging to the last piece of cake on Earth.
"DA!" he declared proudly.
"…Looks like he doesn't wanna go," Oga said smugly, folding his arms. His demon-face returned like it was ready for round two. "Guess you're out of luck, Gothic Umbrella."
"Such an evil look," Furuichi muttered. "Why does that baby love it?!"
Hilda didn't flinch. "Young Master, please let go. We must return. Now."
She reached forward and politely tried to pry the baby off Oga.
"Umm… Hilda, was it?" Yuji asked, waving awkwardly. "I'm sure this is all a misunderstanding, maybe we could just—"
"Let go, Young Master," Hilda said, tugging harder.
The baby: Still clinging.
Hilda: Tug intensifies.
Oga: Smirking, arms crossed like he was watching a soap opera.
Yuji: "Hey Oga, she's trying to take the kid back home! Why are you laughing?!"
"I dunno, it's kinda funny," Oga said with a shrug.
Then the baby opened his mouth—
And everyone got electrocuted.
A crackle of demonic lightning exploded outward like the worst group hug in existence. Sparks zapped their hair into cartoon static, clothes smoked slightly, and even Hilda's perfect parasol got singed at the edges.
"AAAAAAAAAAHHHHHHH—"
ZAP.
A few seconds later, the teens lay twitching on the ground like overcooked fish sticks.
Yuji coughed. "Did... the baby just use lightning?"
Furuichi was upside-down against a wall. "I... I think I saw my ancestors. They're mad at me."
Hilda adjusted her hair without missing a beat and curtsied. "Allow me to introduce myself properly. I am Hildegarde, a maid and servant of the demon royal household. That child clinging to you with suspicious fondness is none other than the next Demon King."
"...Wait. Demon?!" Yuji asked, blinking hard.
"Yes," Hilda said with dramatic flair, "the heir to the demon world's throne. His true name is…"
She paused. The wind blew. Thunder cracked.
"Kaiser de Emperana Beelzebub IV."
Oga, Yuji, and Furuichi all stood still.
Blank faces. No words.
Then—
"…Kaiser de wha?" Oga asked.
"Is that a baby or an RPG final boss?" Yuji added.