When he opened his eyes, an unfamiliar ceiling greeted him.
Right. New life. Let's see what it offers me.
He sat up—and immediately his hand slipped on the sheets.
"Ugh—"
His arm buckled at an angle he wasn't expecting. His center of gravity lurched forward and he had to catch himself before tumbling face-first off the bed.
—damn it. Even though I know I'm four years old, experiencing it is a different matter entirely…
He looked down at his hands.
They're small and soft, with chubby fingers that looked like they belonged on a doll.
When he flexed them, they moved, but the response time felt off—like there was a quarter-second delay between thought and action. While it's not enough to be debilitating, it is enough to be noticeably off.
It's like someone swapped out my keyboard for one with mushier switches… I'll need to get used to this, fast.
He slid off the bed carefully, planting his feet on the floor. His legs didn't quite reach the way he expected them to. When he stood, the room looked taller. The doorknob was higher than it should be.
Everything's scaled wrong.
A knock at the door rang out.
"Kaito-kun? Are you awake?"
Without waiting for his answer, the door opened, and a woman leaned in. She had dark hair tied back in a ponytail, warm eyes, and a gentle smile. He recognized her immediately.
That should be Mori Yuki—my mother.
If the kid's memories aren't failing me, she should be an elementary school teacher with a quirk related to her soothing voice.
For some reason, her voice was unnaturally calming to hear. He could tell that much from the fragments of memory and instinct that belonged to the original Kaito.
Oh well. I'll have to act for now.
Kaito put on a wide smile. "Morning, Mama!"
Still… this is disgusting.
Inside, he was a twenty-five-year-old man. Acting like a small child was deeply uncomfortable. Worse, he worried that he might be overdoing it—that his behavior would come off as forced.
He had plenty of experience pretending, deceiving people in his previous life, but none of it had ever required him to act like a child.
Fortunately, though, his performance seemed convincing enough.
Yuki's smile widened. "Good morning, sweetie! I made your favorite breakfast tamagoyaki!"
That's not my favorite breakfast but okay.
"Yay!" He padded toward her, adjusting his stride mid-step when he tripped over his own feet.
"—Ah! Careful!" she exclaimed.
After that small tragedy, his mother carried him into the dining area. From there, he could see into the kitchen.
It was small and lived-in. Family photos were stuck to the fridge, a well-worn coffee maker sat on the counter, and a calendar was covered in crayon drawings.
Yuki lifted him into a chair and set a plate in front of him.
On it sat neatly cut pieces of tamagoyaki, a bowl of rice, pickled vegetables, and a plastic cup of orange juice decorated with a cartoon hero.
How childish…
That was what his inner, grumpy uncle thought—but the reality was that he was a child.
He picked up the chopsticks.
His fingers didn't grip them quite right. The angle was wrong. His pinky kept slipping off.
He adjusted his grip, tried again. It's better now. He managed to snag a piece of egg, brought it to his mouth—success.
"Good job, Kaito-kun! You're getting so good with your chopsticks!"
What a sad thing to celebrate…
An hour later, a man came through the front door. He looked to be in his late twenties, slightly tired, dressed in a business suit.
Mori Takeshi… What a coincidence. My former name is also Takeshi.
He was supposed to be his father. Kaito had no idea what the man actually did for a living.
"I'm home! I forgot my briefcase—" He spotted Kaito on the floor. "Hey, buddy!"
"Papa!" Kaito scrambled to his feet and ran over—carefully, because his legs still didn't quite work the way his brain expected and he nearly crashed into the coffee table.
Takeshi scooped him up in a hug. "Were you good for Mama this morning?"
"Uh-huh!"
"That's my boy." He ruffled Kaito's hair and set him down. "Papa has to go back to work, but I'll be home for dinner, okay?"
"Okay!"
Takeshi grabbed his briefcase from the counter, kissed Yuki on the cheek, and headed back out the door.
***
Three days passed.
Kaito settled into a routine: wake up, breakfast, playtime, lunch, nap—which he repurposed as thinking time—more playtime, dinner, bath, and bed.
He learned to modulate his behavior. Too quiet and Yuki worried. Too energetic and she got suspicious. He needed to maintain a baseline of "normal four-year-old" that didn't raise any flags.
The hardest part wasn't the physical limitations.
It was the boredom.
Playing with toys was mind-numbing. Picture books were insultingly simple. Children's TV shows made him want to claw his eyes out.
This is torture.
But he endured it, because the alternative was being discovered, and being discovered meant labs and experiments and dissection.
On the fourth day, his father brought someone home.
"Kaito-kun! Come meet Papa's friend's daughter!"
Kaito looked up from the building blocks he'd been pretending to find fascinating for the past twenty minutes.
Standing in the doorway next to his father was another man—younger, maybe mid-twenties, wearing oil-stained work clothes and safety goggles pushed up on his forehead. And clinging to his leg was a little girl with wild pink hair that looked like it had never met a brush in her life.
She had golden eyes that were... uncomfortably intense for a four-year-old.
…Wait, I know her.
Hatsume-whatever-her-name. That tactless engineering girl.
He'd seen the pink-haired girl around the neighborhood a few times over the past week. She was usually covered in dirt or grease or both, and her father was constantly chasing after her as she tried to dismantle playground equipment "to see how it works."
"This is Hatsume-san and his daughter, Mei-chan!" Takeshi announced cheerfully. "Mei-chan is the same age as you! Kaito, why don't you show Mei-chan your toys?"
I'd rather eat glass.
Kaito grimaced internally. The Hatsume type was the kind of person he avoided. They were always hard to talk to, completely absorbed in their own world. Dealing with even one of them usually left him utterly drained.
That said, he didn't really get a choice.
"Okay, Papa!" Kaito chirped, putting on his best good boy smile.
Mei—whom he'd only ever seen from a distance—immediately let go of her father and marched straight toward him with the confidence of a tiny warlord.
"HI! I'M MEI!" she announced at a completely unnecessary volume.
I know. Everyone within a three-block radius knows. You're not exactly subtle, little Hatsume.
"Hi! I'm Kaito!" he replied with equally fake enthusiasm, matching her energy level.
Instead of responding, Mei dropped to her knees in front of his block tower—the one he'd been carefully constructing for the past hour—and immediately began dismantling it.
Hey. HEY. That took me an HOUR to make! Not because I need that much time to build it—but I need to pretend as if it is. And did you just—
"These blocks are boring!" she declared, scattering them everywhere.
Kaito's hand twitched uncontrollably.
Deep breaths, Kaito. She's four years old. Whatever you're thinking right now, that's frowned upon in society.
"We should make something better!" Mei's eyes lit up.
"...What do you want to make?"
"A ROBOT!"
Out of wooden blocks? Uh, simulations are a thing. And she's a kid. I guess that's fine.
The adults had migrated to the kitchen, leaving the two children alone. Kaito could hear his mother offering tea, Hatsume-san apologizing for Mei's energy levels.
You should apologize. Your daughter is a natural disaster in human form.
Meanwhile, Mei was already attempting to construct something that defied the structural integrity of children's building blocks.
"See, if we put this here—" She balanced three blocks on top of each other at an angle that should not have worked. "—and this here—"
The tower immediately collapsed.
"Hmm." Mei frowned at the fallen blocks.
Kaito watched for a moment, then picked up one of the blocks. "Maybe it fell 'cause it's too skinny at the bottom?"
Please let that sound like a four-year-old observation.
Mei looked at him, then at the blocks. "Skinny?"
"Yeah! Like..." Kaito arranged a few blocks in a wider base. "Fat on the bottom, then smaller on top! Like a triangle!"
Basic center of gravity. Wrapped in preschool vocabulary. Nailed it.
"OHHH!" Mei's eyes lit up. "The bottom needs to be BIGGER! That's so smart, Kaito-kun!"
She immediately started rebuilding with a wider foundation, her hands moving quickly.
It still looked questionable, but at least it wouldn't collapse immediately.
"But it needs more support structure! Do you have any tape?"
Kaito wondered how she even knew what a support structure was at their supposed age.
"Why do you need tape?" he asked.
"To make it better!"
"I don't think Mama will let us use tape on the blocks…"
"Why not?"
"Because she says so?"
Mei pouted—actually pouted. Her cheeks puffed out and everything.
"Fine," she huffed. "We'll do it without tape. But it won't be as cool."
She went back to building... something. Kaito couldn't tell what it was supposed to be.
"Hmm... not a lot to work with. But we can make do! Let's build a castle!"
…Well. That sounds harmless enough.
This was, without question, the exact moment he should have stopped assuming.
***
A/N: The interactions will continue. Let me know if they start feeling overdone—when it comes to writing banter, I tend to get a bit carried away.
I'm still not great at talking to people in real life, but I've always loved writing dialogue-driven stories. I even wrote fanfics for Makeine, Saekano, and Roshidere back then, though they were short-lived and not posted on this platform.
Rate it from 1–10, with reasoning if possible. That would really help me figure out what's missing from the story.