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Atsushi Nakajima had many habits—some good, some questionable, some born from trauma, and some born from the quiet, desperate love he held for the only family he had left. But there was one habit no one ever questioned, one that he clung to with a fierceness even he didn’t fully understand:
Whenever he received his paycheck, he set aside 25% of it for Kyouka. Always.
Not a yen less.
Not a yen more.
Exactly a quarter.
At first, he didn’t tell anyone. Not Kunikida, who would’ve praised his budgeting but lectured him about miscalculations. Not Yosano, who already spoiled Kyouka in her own ways. Not even Kyouka herself, who simply assumed Atsushi was… generous. In reality, Atsushi was terrified she’d refuse if she knew the truth.
It started the month she officially joined the Armed Detective Agency.
Atsushi remembered sitting at his desk, staring at his bank account on his phone. It wasn’t much—his salary never felt like enough. There were rent costs, food, the occasional medical bill (which Yosano mostly waved away), and emergencies he was somehow always involved in.
But when he thought of Kyouka—small, quiet, trying so hard to fit into a life she’d never been allowed to have—something in him tightened.
She hadn’t had a childhood.
Neither had he.
And Atsushi decided, with all the stubbornness of someone who’d grown up starved for warmth, that while he couldn’t fix his own past, he could help hers.
So he did what any responsible, newly financially independent adult did:
He googled “How much money should you set aside to spoil your little sister?”
The internet gave him many ridiculous answers.
Atsushi ignored all of them.
He settled on 25%.
Round, neat, reasonable.
A promise.
And it changed everything.
“Hey, Kyouka,” Atsushi called awkwardly one evening, hovering at her doorway like a cat uncertain if it’s allowed inside.
Kyouka looked up from her homework, blinking. “Yes?”
He swallowed. “Do you want to, um… go out tomorrow? Get something? Anything. Your choice.”
She tilted her head. “Like… what?”
Oh no. She sounded confused.
She didn’t know what it meant to be taken out simply because someone wanted to make her happy.
Atsushi forced a smile. “Well, tomorrow’s Saturday! Ice cream? New headphones? A—uh—stuffed rabbit?”
Her eyes softened in a way that nearly crushed him. “Stuffed rabbit.”
“Then a stuffed rabbit it is!”
He bought her three.
He told her the buy-two-get-one-free sale saved him money.
There was no sale.
It didn’t take long for patterns to emerge.
Month 2: She wanted a new kimono because she had never chosen her own before. Atsushi spent an hour pretending the price tags didn’t scare him. Kyouka picked a simple one with plum-blossom details. “It’s okay if we can’t,” she said softly when she saw the price.
Atsushi bought it anyway.
Month 4: She stopped by his room at midnight, clutching a notebook for school. “Atsushi… can we get coloured pencils tomorrow?” He nearly cried at the way she asked—as if she expected him to deny her. He bought her the expensive 72-color set.
Month 6: She confessed she wanted to try roller skating. Atsushi fell six times the next day. She laughed, really laughed, and he decided broken bones were worth it.
Month 9: Christmas came. She shyly said she wanted a music box. He found an antique one that played a lullaby she didn’t know, but loved instantly.
Every month—25%.
Every month—something for her.
Sometimes it was a big thing.
Sometimes it was small.
Sometimes she didn’t ask for anything, and he’d surprise her with strawberry mochi or a book with a pretty cover. She always said thank you, always hugged him with the gentleness of a girl learning soft things for the first time.
And Atsushi?
He learned what it felt like to give someone the childhood he never had.
Kyouka discovered the truth accidentally.
It was late—past midnight. Atsushi was sitting in the common room with Kunikida, the two reviewing receipts because Atsushi had messed up a reimbursement form (of course he had). Kyouka walked in quietly, unnoticed, until she heard:
“…and here—this is a quarter of your income. Did you mean to allocate exactly 25% of your monthly salary to discretionary spending labelled ‘Kyouka’? Atsushi, this is a strangely consistent pattern.”
Atsushi panicked. Kunikida blinked. Kyouka froze behind the doorway.
Atsushi weakly laughed. “O-oh, that? Haha. Um. It’s nothing! Budgeting! You know me! Very adult.”
“You’re terrible at budgeting,” Kunikida deadpanned.
“Okay, fair.”
Kyouka stepped into view. “Atsushi… why 25%?”
His soul left his body.
“Kyouka! H-hey! Uh. You heard that?”
She nodded.
He rubbed the back of his neck, flushing. “I… just wanted you to have things I—things we never got to have. A normal childhood. Stuff kids should get. Even small things like choosing your own snacks or clothes. You deserve it, so I just…”
He swallowed hard.
“I guess I made a rule. For myself.”
Kyouka looked at him—really looked.
With the kind of gaze that saw through people.
Then she walked forward, quietly, and hugged him around the waist.
“Atsushi,” she murmured into his shirt, “you gave me more than a childhood. You gave me a home.”
He felt his throat close.
“I don’t need more things,” she continued. “I only need you.”
He trembled, holding her tight.
Kunikida wiped his glasses with suspicious intensity.
Even after she knew, Atsushi still did it.
Why?
Because every time he saw Kyouka walk through a store aisle without fear, or try something new, or smile at a silly trinket, or laugh at a stuffed bunny—
He felt something warm and unfamiliar bloom in his chest.
Pride.
Love.
Joy.
Family.
So he continued setting aside 25%, not because he had to, but because he wanted to honor the promise he made that first month:
If he could help rewrite even a piece of her story, he would.
And Kyouka, knowing this, never misused it, never demanded anything.
Sometimes she only asked for a book or a new tea flavor.
Sometimes she asked for nothing at all.
Sometimes she used the money to buy Atsushi a gift instead.
One month she bought him a sweater.
Another, a new pen.
Once, she bought matching keychains shaped like little white tigers.
She said, “So you won’t forget that you aren’t alone.”
Atsushi cried in the convenience store parking lot for ten minutes.
In the end,
Kyouka had her childhood—belated, fragile, healing.
And Atsushi?
He got to watch her grow.
He got to support her.
He got to be the big brother he wished someone had been for him.
Twenty-five percent of his paycheck was a small price to pay for that.
A tiny number for something priceless.
A habit he would carry for the rest of his life.
Because family wasn’t something he was born into.
It was something he chose to build—with her.