“Ding-dong.”

The doorbell rang.

I glanced at the clock.

It wasn’t even ten yet.

…Who could that be?

Mom had gone shopping, and it was far too early for a delivery.

I headed to the front door.

Through the frosted glass, I could make out the silhouette of a slender figure.

Small build.

Hair that reached about shoulder length.

…Wait.

No way.

“…You’ve got to be kidding me.”

I opened the door.

Standing there was exactly who I had feared—and hoped—it would be.

“Morning, Kyoichi!

I’m not late, am I?”

The girl greeted me with a bright smile and a cheerful wave.

It was my childhood friend, Shiraishi Mio.

“…Uh… did you need something?”

“Huh?

We promised we’d do our spring break homework together, remember?”

“…We did?”

“What?

Did you forget?

Yesterday, on our way home, I asked, ‘Can I come over tomorrow morning?'”

“Ah…

Ah…

Yeah…

I guess you did say something like that…”

Inside, I was panicking.

I’d only just been reincarnated.

Of course I had no idea what plans I’d made recently.

This was bad.

Still, she was already here.

Nothing I could do about it now.

“F-For now, you can use the living room.

Mom’s out.”

“Okay, thanks!”

She stepped inside with practiced familiarity, took off her shoes, and headed straight for the living room.

It was obvious she was used to coming here.

Actually…

She really was a regular.

I followed her into the living room.

She set her backpack beside the table and immediately started taking out her notebooks.

“Alright, let’s start with math today.”

“O-Okay…”

“What’s with that reaction?

You sound totally unmotivated!”

“No, it’s not like that…”

The truth was that I couldn’t even remember making this promise, so I had no idea how I was supposed to react.

All I could do was laugh awkwardly.

“Here.

We were starting from this page, right?”

“Y-Yeah…

Probably.”

Mio opened her notebook and started writing with her pencil.

Watching her lean forward over the table filled me with a strange sense of nostalgia.

She hadn’t changed at all.

Her silky hair swayed gently, briefly revealing the curve of her ear.

She was energetic and cheerful.

At the same time, she had an almost puppy-like quality about her and was surprisingly good at reading people’s expressions.

She wasn’t the flashy type.

She simply had the kind of natural cuteness that quietly drew people’s attention.

“What are you spacing out for?

You haven’t done anything.”

“I’m observing.

It’s observational learning.”

“That’s just another word for slacking off!”

She lightly smacked my shoulder with her notebook.

Well, it was only middle school math.

Even though it had been over ten years, I’d studied high school mathematics.

This would be easy.

These little exchanges hadn’t changed either.

Back in elementary school, we used to study together all the time.

Homework always went faster that way.

More importantly, it was fun.

Mio was the one who always insisted on coming over.

Those memories…

To the current me, they weren’t just childhood memories anymore.

They were memories from a previous life.

Maybe that was why the Mio sitting in front of me seemed to shine just a little brighter.

“Come to think of it, we’re about to become third-year middle school students.

Doesn’t that feel crazy?”

“Yeah.

We’ll be preparing for high school entrance exams.”

“Entrance exams…

It still doesn’t feel real.

Do you think the serious students have already started studying?”

“I’m sure some have.

The ones going to cram school are probably already working hard.”

“Ugh…

Now I’m getting nervous…”

Even while talking, her pencil never stopped moving.

That was one of Mio’s strengths.

It wasn’t that she was especially talented.

She was simply the type who always got things done in the end.

She could be a little absentminded and emotional, but she worked steadily and had a solid core.

“…Still, you seem a little different today, Kyoichi.”

And she was sharper than she looked.

“Huh?”

“I don’t know…

The way you talk.

The way you look at things.

You seem calmer somehow.”

“O-Oh.

Maybe it’s puberty?”

“Oh?

So puberty turns people into adults?

That’s convenient.”

She laughed as she joked.

But her eyes never left mine.

Uh-oh.

She was probably half serious.

She really was the type who noticed when something changed.

If I wasn’t careful, she might actually realize I’d been reincarnated.

Choosing my words carefully, I answered.

“Well…

Spring break’s given me a little more time to think.”

“Hmm.

I guess that makes sense.”

She accepted the explanation surprisingly easily.

Still, I couldn’t tell what she was really thinking.

Maybe…

She’d already realized I wasn’t quite the same Kyoichi anymore.

“Hold on.

Isn’t this problem kind of hard…?”

Mio stopped writing and turned her notebook toward me.

“Let’s see…

Oh, it’s a word problem.”

“Exactly!

The one that says x + y = 100 and x:y = 2:3.

Once I see that, I have no idea what to do anymore…”

“I see.”

The solution immediately came to mind.

It was one of those classic problems that appeared constantly on high school entrance exams.

I’d explained it countless times back when I worked part-time as a cram school tutor in my previous life.

“In this case, since the ratio of x to y is 2:3, the total number of parts is five.

If five parts equal one hundred, then x is forty and y is sixty.

The calculation goes like this…”

“Whoa!

That was fast!

And it actually makes sense!”

Mio’s eyes widened as she hurriedly copied everything into her notebook.

“Were you always this smart, Kyoichi?”

“…Who knows?”

I hadn’t expected that question.

For a moment, I didn’t know how to answer.

As far as I remembered, I had been an above-average student in middle school.

I wasn’t particularly brilliant.

I paid attention in class, did my homework, and got decent grades.

But now…

I had the memories of a thirty-four-year-old.

I’d graduated from university.

Learned plenty over the years.

And on top of that…

I had access to AI.

“I’ve just been taking studying a little more seriously lately.”

I answered vaguely.

Apparently satisfied, Mio nodded.

“I see.

You looked kind of cool just now.”

“…Seriously?”

“Just kidding!

I’m kidding!”

She laughed as she said it.

It clearly sounded like a joke.

But for just a split second…

It looked as though she had blushed ever so slightly.

For some reason, my heart skipped a beat.

After that, we quietly focused on solving the rest of the problems.

The only sounds filling the living room were the scratching of our pencils and the spring breeze drifting through the window.

It was surprisingly peaceful.

Time slipped by before either of us noticed.

Soon, nearly every worksheet on the table was covered with check marks.

“…Finally!

We’re done with math!”

Stretching her arms, Mio flopped backward onto the sofa.

“Now we’ve just got English, science, and that research assignment left.”

“Right…

About that research assignment…”

She sat back up with a troubled expression.

“The one where we’re supposed to research local history and summarize it on an A4 sheet.

I’m seriously terrible at those…”

“Yeah…

I remember.”

I vaguely recalled digging through local history books in the library and piecing together information from the city’s website.

“I can never find the right information.

I don’t know how to organize it.

And if I just copy and paste stuff, the teacher will probably notice.”

“I know exactly what you mean.”

Back then, whenever they assigned local history, I always thought, ‘Who even cares about this?’

But things were different now.

I had…

ChatGPT.

“Alright.

Let me take a look.

What topic did you get?”

“Something like the history of Hachioji City or its traditional local products.”

“Okay.

Give me a minute.”

I stood up and casually headed to the computer in the next room.

Naturally, I left the door half closed so she couldn’t see inside from the living room.

Opening ChatGPT, I quickly typed my request.

Summarize the history of Hachioji City in about 800 words using language that is easy for middle school students to understand.

[ChatGPT]

[Hachioji City prospered as a post town during the Edo period…]

“Perfect.”

It looked great.

I made a few small edits so it sounded a little more like something a middle school student would write.

That alone made it feel completely original.

Then I copied the text into Word and printed it out.

“Here.”

“Huh?

What’s this…?

Wait, you’re already done?”

“I put this together for myself yesterday.

You can use it.

I’ll just write another one.”

“W-Wow…

Seriously?

Thanks!

This helps a lot!”

Still looking astonished, Mio eagerly read through the report ChatGPT had written.

“The writing’s really easy to understand, and it actually sounds like something I’d write myself.

The teacher won’t notice, right?”

“…Probably.”

Honestly, it was polished enough that even the Board of Education wouldn’t have found anything to complain about.

Still, seeing Mio smile with relief was enough for me.

“…You’ve really changed, Kyoichi.”

“…You think so?”

“Yeah.

The old you would’ve probably said, ‘Go research it yourself.'”

“Was I really like that?”

“A little.”

She smiled softly.

For some reason, seeing that expression made my heart race again.

Maybe…

There were things that changed little by little during ordinary days.

My actions.

Mio’s expressions.

The distance between us.

Perhaps I was finally beginning to notice the things that had always mattered… but that I’d overlooked before.