Chapter Text
Dazai’s third year was a blur of legalities.
Some shallow admissions on his end, a bunch of threats from Mori, a long string of mandatory sessions with the newly hired counselor that McGonagall had brought in, the call for arrest and the narrow escape of a Port Mafia boss, and, somewhere tangled in the middle of all that chaos, an adoption process.
Dazai stared at the parchment for a long while after it was signed. If Snape hadn’t known any better, he might have assumed the boy was reading a fascinating book rather than holding a contract.
Dazai knew a lot about contracts.
Contracts were shackles disguised as agreements. They were invisible leashes tied carefully around a person’s throat, pulled whenever someone higher in the hierarchy decided it was time.
The Port Mafia ran on them.
He had signed many before but this one felt different.
It was strange to see his name beside another.
Not Mori’s.
Not his father's
Not the Port Mafia's.
Just a name written in careful, angular script.
Severus Snape.
By the time his miraculous fourth year at Hogwarts began, Dazai Osamu was Snape’s son.
Snape’s cabin sat deep within a stretch of forest in the middle of nowhere, tucked into a pocket of tall pines that whispered constantly when the wind moved through them.
The place was practical, and clearly built for one person.
One bed.
One couch.
One table.
One narrow shelf of books stacked two rows deep.
The only thing that seemed to exist in abundance was mugs.
Ceramic mugs filled the shelves, the counters, even the windowsill.
Dazai found it strange.
The boy had spent most of his life surrounded by people. The Port Mafia headquarters had been loud even at night, polluted with the noise of footsteps, distant arguments, the low hum of operations that never truly stopped.
Hogwarts was the same in its own way. Students everywhere, voices echoing through stone corridors. Movement, always movement.
The cabin breathed quietly around them.
Dazai sat cross-legged on the couch early one morning, the late summer sunlight filtering through the tall windows in pale golden bands.
Dust motes drifted lazily through the light.
He was wearing the pajamas Snape had given him.
That alone was surreal.
Dazai had fully intended never to wear them again after the first night he'd been handed them, something about accepting them had felt dangerously close to admitting permanence.
And permanence had never been kind to him.
Yet here he was, barefoot, hair messy, wearing the oversized clothing on a slow morning like it was the most normal thing in the world.
A kettle whistled softly from the kitchen.
Snape moved through the small space with the quiet efficiency of someone who had lived alone for decades. He poured hot water into one of the many mugs and stirred something sweet into it without looking up.
Dazai watched him with the kind of casual curiosity one might use to observe an unfamiliar animal.
Living with Snape was… odd.
The man wasn’t warm, he wasn’t particularly expressive, but there was a steady consistency to him that Dazai had never experienced before.
Snape woke early.
Snape made tea.
Snape read.
Snape cooked simple meals and expected them to be eaten.
It was predictable.
Predictable things were usually traps, but this didn’t feel like one.
Not yet.
Snape set the kettle aside and finally spoke without turning.
The man carried his mug to the table and sat down with a stack of parchment.
Some documents were Hogwarts administrative letters, others clearly Ministry forms still related to the aftermath of Mori’s escape.
The air shifted slightly, handled with grim competence.
After a moment, he spoke again.
“There is something we must address before the school term begins.”
Dazai leaned sideways against the couch arm, listening.
Snape folded his hands.
“I have no intention of allowing Hogwarts to become a circus,” he said flatly. “Nor will I permit the Daily Prophet to invent scandals for their entertainment.”
Ah.
Politics.
Dazai’s smile widened faintly.
“Students already talk,” Snape continued. “Speculation regarding your presence in Slytherin, your… unusual circumstances, and the ridiculous rumor that I am your father.”
Dazai tilted his head.
Technically not a rumor anymore.
Snape’s dark eyes lifted.
“For the sake of avoiding nepotism accusations and unnecessary complications,” he said carefully, “our arrangement will remain private.”
A pause.
“Within the school I remain your professor.”
Another pause.
“You will address me accordingly.”
Silence settled briefly in the room.
Then Dazai’s smile bloomed like mischief finding sunlight.
He stood up from the couch with theatrical obedience.
His voice turned bright.
“Yes, Professor.”
The Hogwarts Express was loud, voices spilled through the corridors, luggage thumped.
But after a summer spent in a cabin where the loudest thing had been wind moving through pine trees, Dazai almost welcomed it.
Near the center of the train, a compartment door slid open with a bang.
“Well, well, well—”
“—look who’s crawled back from the grave.”
The two voices overlapped perfectly.
Fred and George leaned dramatically into the doorway like a pair of investigators who had just discovered the subject of a very interesting crime.
Curled lazily across the seat by the window sat Dazai. “Hello.”
“You vanished!” Fred said, pointing accusingly.
“For months!” George added.
“People thought you'd been expelled—”
“—Or murdered.”
“Or both!”
Dazai tilted his head.
“I’m honored that you considered both possibilities equally likely.”
The corridor outside the compartment filled quickly once the door slid open.
Behind the twins came three familiar Slytherins.
Blaise leaned against the doorframe, ehind him, Pansy was fiddling with the chess piece she wore as a necklace with an amused smirk, while Draco Malfoy stood a little straighter than usual, trying very hard to look like he hadn't hurried down the corridor the moment the information about Dazai reached him.
For a moment no one spoke.
Blaise broke the silence first.
“You didn’t write.” His tone wasn’t angry, just quietly reproachful. “Not once.”
Dazai blinked slowly.
“That’s not true.”
Five heads lifted.
“I wrote several letters.”
George leaned forward eagerly. “You did?”
“Yes.”
Dazai sighed and shrugged.
“I simply never sent them.”
Fred put a hand over his heart in theatrical pain.
“That’s worse.”
Pansy huffed a laugh.
“Oh please, you two act like you were the only ones sulking.” She tilted her head toward the blond beside her. “Draco and Blaise were sighing all year long.”
Draco snapped instantly.
“I was not!”
“You absolutely were.”
Draco shot her a glare sharp enough to slice parchment.
Meanwhile Dazai remained exactly where he was,curled against the window, chin resting on his hand, watching the exchange like someone enjoying a particularly entertaining play.
The train rattled forward along the tracks.
Outside the window the countryside rolled by in long green strokes.
Dazai’s third year had been… strange.
He had barely attended classes.
Most of the time he had been excused entirely, whether about legal meetings, counseling appointments, and paperwork that no student should have to fully understand.
Yet when finals arrived, Dazai had simply walked in, taken the written examinations, and walked back out with perfect scores in every subject.
Except the practical exams, which he had skipped with the same casual indifference someone might show toward a rainy afternoon.
With the several hundreds of special exemptions made for his situation, Dazai managed to barely move up to the fourth year with the rest of his batch.
George leaned across the seat.
“So where were you all year anyway, Snakey?”
Dazai smiled.
“Here and there.”
“That tells us nothing.”
Blaise suddenly leaned forward, eyes glittering with curiosity.
“Actually, there’s a rumor going around.”
The compartment stilled.
Even Draco looked interested now.
Fred’s grin widened slowly.
“Oh yes,” he said.
“That rumor.”
George clapped his hands together.
All pairs of eyes turned toward Dazai.
George spoke first.
“Is it true—”
Fred finished the sentence with relish.
“—that Professor Snape adopted you?”
Silence.
The wheels of the train clattered steadily beneath them.
Dazai’s expression did not change.
He simply tilted his head slightly and smiled.
Not an answer nor a denial, just that infuriatingly pleased little smile.
Fred grabbed George’s sleeve.
“Did you see that?!”
George pointed.
“That was a yes smile!”
“It was not—”
“It absolutely was!”
Blaise narrowed his eyes at Dazai.
“You’re doing that thing.”
Dazai clasped his hands together thoughtfully.
“Doing what?”
“Not answering.”
“Really now?” Dazai said lightly.
Fred groaned dramatically.
“You can’t just leave it there!”
George dropped into the seat beside him.
“We need an answer!”
Dazai looked around the compartment slowly.
He hummed softly.
“Well…”
Then he stood up smoothly, stretching like a cat waking from a long nap.
Dazai shrugged, “You’ll find out.”
Fred choked.
George grabbed his shoulders.
Dazai managed to slip past them into the corridor.
Behind him chaos erupted instantly.
“You little menace—”
“Come back here!”
“DAZAI!”
Dazai walked down the train with his hands in his pockets and a pleased smile.
After a year filled with lawyers, counselors, threats from the Port Mafia, and endless paperwork…
He finally had free time again.
And if there was one thing Dazai Osamu enjoyed
It was a good mystery.
Which meant that for the foreseeable future, Hogwarts had just been handed one.
Students crowded the hall, voices overlapping, books clutched against chests.
Among them was Dazai with the small, loosely organized group that had somehow formed around him during the previous year, Hell's Hound.
They chatted idly amongst themselves but Dazai wasn't paying much attention.
He had spotted something interesting ahead.
A tall black figure striding down the hall like a thundercloud with legs.
Professor Snape.
Dazai’s mind clicked instantly.
He waited until the professor passed directly beside them.
Then, in a perfectly calm voice—
“Good morning, Dad.”
The hallway went silent.
Snape stopped.
Then the man sharply turned his head.
For a moment, no one spoke.
Even Fred and George's loud laughing had halted.
Snape’s voice came out low and dangerous.
“…Detention.”
Dazai smiled politely.
“Yes, Dad.”
A choking noise came from Snape that might have been a cough.
“Mr. Dazai,” Snape said with deadly precision, “one more word and I will ensure your detention lasts until the end of the term.”
Dazai nodded thoughtfully.
Snape stalked away.
The moment he turned the corner Fred screamed.
“YOU CALLED SNAPE WHAT?!”
Two days later, a package arrived in Snape’s office.
It had no sender, which was already suspicious.
Snape stared at it with deep distrust before finally opening the paper wrapping.
Inside was a mug.
That wasn't unusual, Snape owned many mugs.
Students had developed a strange tradition of gifting them to him as seen by the one Dazai had taken into custody that read: “World’s Okayest Professor.”
He lifted the new mug slowly.
This one read: “World’s Okayest Dad.”
Snape stared at it in almost disbelief, then he placed the mug on the far edge of the desk, as if it might bite him.
There was a knock at the door, Snape didn’t even look up.
“Enter.”
The door opened.
Dazai stepped inside.
“Oh good,” Dazai said cheerfully. “It arrived!”
Snape pinched the bridge of his nose.
“Mr. Dazai.”
“Yes?”
“If you ever refer to me as ‘dad’ again within school grounds again, I will personally ensure you spend every weekend of the year in detention.”
Dazai tilted his head.
“Understood.”
Pause.
“…Father.”
Snape looked like he might strangle someone.
“Out.”
A few days later, the Hell’s Hound occupied their usual table in the Great Hall.
Dazai leaned back in his chair, explaining something while Ron and Hermione listened.
“Well,” Dazai said thoughtfully, “then my dad—”
He paused.
“Oh. No, wait.”
He corrected himself smoothly.
“When Professor Snape demonstrated the correct method—”
Behind him, footsteps stopped and the table froze.
Snape stood directly behind Dazai with the expression that of a man reconsidering his entire career.
Ron looked like he wanted to vanish.
Snape spoke slowly.
“…Ten points from Slytherin.”
Draco sat up. “What?!”
Snape promptly left.
By the end of the week, Snape had developed a headache.
A very specific headache caused by one particular student.
He pushed open the doors to the hospital wing.
Pomfrey looked up immediately. "Severus, what—”
Snape stopped.
Because on the nearest bed sat Dazai with a small scrape across his cheek.
Pomfrey was cleaning the cut.
Dazai brightened instantly. “Oh, hi dad!”
Snape stared at the ceiling for a long moment. “Something for a headache.” he said flatly.
Pomfrey frowned slightly but handed him a vial.
Snape looked at the boy,
Then at Pomfrey,
Then back at Dazai.
“Mr. Dazai,” he said tiredly, “if you address me that way again, I will assign you detention until graduation.”
Dazai hummed thoughtfully.
“Yes, Dad.”
Snape downed the vial in one swallow.
The rumor began as a ripple.
Then it became a wave.
Within three days of Osamu Dazai’s return to Hogwarts, the castle’s usual gossip networks. Ravenclaw study tables, Slytherin ad Gryffindor common room whispers, they had all strengthened the theory so outrageous that it refused to die:
Professor Severus Snape had somehow adopted Osamu Dazai.
No one knew if it was true.
That, of course, made it irresistible.
And Dazai was enjoying every second of it.
The hallway was packed, students between classes, bags slung over shoulders, parchment clutched under arms. In the middle of that walked Snape, robes cutting through the crowd like a black sail.
He almost made it through unnoticed.
Almost.
Dazai spotted him immediately.
Like iron to a magnet, he drifted over, falling into step beside him with hands tucked casually into his coat sleeves.
“Dad?”
Snape kept walking.
“Hey, daaad?”
Still nothing.
Several heads turned.
Dazai leaned slightly into Snape’s personal space, peering up at him with exaggerated curiosity.
“Helloooo?”
A group of second-years slowed down. A pair of Hufflepuffs stopped outright. Someone near the wall whispered something that made another student choke on a laugh.
Snape’s eye twitched.
He continued forward, refusing to acknowledge the boy glued to his side.
Dazai persisted.
“Father? Paternal figure? Guardian of my emotional well—”
Snape’s stride lengthened.
Dazai matched it effortlessly.
Behind them the whispers grew.
“Did he just—?”
“He called him dad again—”
“No way—”
Then one voice slipped through the murmuring crowd, quiet, amused, and dismissive.
Then a whisper reached Snape's ear.
“Isn’t the Demon just embarrassing himself at this point?”
Snape stopped.
The sudden halt nearly caused the boy to crash into his back.
The corridor quieted.
Snape slowly exhaled through his nose, shoulders rising and falling once as if he were releasing several years of accumulated patience.
Beside him, Dazai tilted his head, watching with bright curiosity.
Snape turned.
His dark eyes settled squarely on the boy.
And in a tone so calm it felt almost surgical, he answered to what Dazai had been repeating all week.
“Yes, son?”
His dream of a peaceful academic year had just died in that corridor.
And judging by the way Dazai looped his arm comfortably through the professor’s sleeve, the boy intended the funeral to be loud.