My grandparents' place was typical of the countryside—a sprawling house whose grounds even included a mountain and a waterfall.

Lush trees grew thick in the garden, which featured a large pond where koi and turtles lived, along with a big storehouse where plenty of valuables were kept. Yet, even on that scale, it was apparently considered on the smaller side for that village.

That was how many massive houses surrounded it.

I believe it was during the summer break of my third-grade year.

My cousin Masaya, who was a year older, Takkun, who was my age and lived nearby, and I were playing hide-and-seek at my grandfather's house.

Inside the vast house were countless places for kids to hide: a shoe cabinet big enough for a child to easily fit into, a telephone room (apparently old houses used to have a room just for placing a phone), and a pantry room from the days when they hired servants—it was full of places that made your heart race just looking at them.

Takkun was it, and when it was time for me and Masaya to hide, Masaya whispered to me, "Come here."

I wondered if he was actually suggesting we hide in the same spot, but he led me to... a small door under the staircase that went up to the attic.

"What do you think this door is?"

Masaya asked with a smirk, but I had no idea.

"I don't know. First time I've ever seen it,"

I replied.

"Me too. I've been to Grandpa's tons of times, but I just found it today."

Saying that, Masaya slowly opened the door.

It made a creaking sound like ancient wood rubbing against metal.

"Huh? We're going in? Let's not."

I said instinctively, but Masaya wouldn't listen.

"It's fine, it's fine. We'll take a quick look and come right back. No one will notice."

Saying that, he stepped past the door into the pitch black.

I couldn't just wait there by myself, so I reluctantly followed after him.

Inside the door, it was like a narrow hallway.

Actually, it was closer to a cave than a hallway.

It felt like an unpaved, long passage that was little more than a dug-out hole.

Masaya, who had somehow brought a small flashlight, pressed forward while shining its unreliable light ahead to guide our way.

Dead rats lying here and there added an eerie touch.

"Hey, how far does this go?"

I asked, clinging to Masaya's clothes.

"Who knows? I've never been in here before either. But my parents and grandparents never said a word about a place like this."

Masaya seemed to think there was "something" ahead that they didn't want kids to see.

"What do you mean, something they don't want kids to see?"

"Well, you know, Grandpa's place has money, but the house is smaller than the others, right? They're probably hiding a whole stash of gold bars and jewels down here."

Looking back now, it was a ridiculous, childish idea, but back then, for some reason, Masaya's words felt oddly convincing.

Thinking of it as a treasure hunt took the edge off my fear, so I pressed deeper and deeper into the tunnel alongside Masaya.

After walking for a while, an old-looking door finally came into view.

"Oh, the finish line!"

Masaya pushed ahead to open the door first.

But what opened up past that door was nothing more than a vast grassy field.

"Huh? What is this place?"

"Who knows... Was there a place like this anywhere near Grandpa's?"

An endless grassy field stretching as far as the eye could see.

You couldn't even see the houses or mountains that should have been around us.

"...What is this? What's going on?"

"Let's just go back for now."

Saying that, Masaya tried to open the door we had come through, but then let out a sharp "Huh?!"

The door that should have been there was gone.

In fact, there was no sign of my grandparents' house either. There was only a vast grassy field stretching out into nothingness.

We couldn't go back...

"Anyway, let me find someone!"

Masaya and I started running, searching everywhere for another person.

But the same identical landscape just kept going, without even a single house in sight.

The sound of cicadas chirping could be heard from somewhere, yet there wasn't even a tall tree to be found.

Was this a dream? Or reality?

My head was spinning from the heat, making it impossible to think straight.

Just then—

"Ah, there! There's a person!"

Masaya waved his arm frantically.

"Excuse me!"

In the direction Masaya was waving, there was an old woman wearing a mustard-yellow kimono.

At Masaya's voice, the old woman turned around.

But something was wrong.

"Masaya! Stop!!"

I shouted in a panic.

The old woman didn't have a face.

To be precise, where her face should have been was a pitch-black void.

"Eek!!"

I grabbed Masaya, who had fallen on his rear in shock, and we bolted at full speed.

Screaming something incomprehensible, the old woman came running straight for us.

In her hand, she was clutching something that looked like a rusted sickle.

"What is this?! What is this?! If this is a dream, wake me up!!"

We ran and ran—how long had we been running?

Before I realized it, a large house came into view.

It was an old house with a thatched roof, but intuition told me it was my grandfather's house from long ago.

Since the back door was closer than the main entrance, we rushed toward it.

But when I tried to pull the sliding door open, my sweaty hands slipped and it just wouldn't open.

"Hey! Hurry! Hurry up!!"

Masaya urged me on.

This was bad—the old woman was going to catch up to us any second.

"Open! Open! What is going on?!"

As I was frantically rattling the door, Masaya—

"AAAHHHH!!!"

—screamed as he charged headlong at the old woman, who had somehow gotten right behind us.

At that exact moment, the sliding door opened, and I tumbled inside. But when I tried to call out to Masaya, the door slammed shut on its own.

"Wait! Masaya is still outside!!"

I tried to reach for the sliding door, but my head was spinning too fast to stand up, and I lost consciousness right there.

"Ah, he's awake!"

When I opened my eyes, I met the gaze of Takkun, who was peering down at me.

I was lying in a Japanese-style room, and my grandmother was fanning me with a paper fan.

My mother brought over an ice pillow with a worried expression.

"Are you okay? How are you feeling?"

"I'm okay... Um, where was I, and what was I doing?"

Takkun stared at me with concern.

"What do you mean? You were playing with me. Then suddenly you said you had to go to the bathroom..."

According to Takkun, while we were playing, I said I needed to use the bathroom and then never came back.

When a worried Takkun looked for me, he found me collapsed, slumped against the back door of the kitchen for some reason.

Back then, the term 'heatstroke' wasn't commonly used, but based on the symptoms, it was likely heatstroke.

"Sorry, my memory is a bit hazy..."

Did I really think I needed to go to the bathroom?

In the first place, the bathroom and the kitchen were in completely opposite directions.

Why would I go toward the kitchen if I was heading for the bathroom?

Maybe I thought about getting a drink of water.

But if that was the case, why was I by the back door?

The back door... The back door... It felt like I was forgetting something...

"Ah!!!"

Because I suddenly shouted at the top of my lungs, Takkun, my mother, and my grandmother all looked at me in shock.

"That's it! That's right—Masaya! Where's Masaya?!"

When I screamed this, my mother and grandmother exchanged glances.

"Masaya? Who is that? Is he a new friend?"

Strangely enough, the very existence of Masaya had completely vanished from everyone's memory.

Even Masaya's parents said things like, "We don't have any children."

But I remembered clearly.

Masaya was definitely real. He, Takkun, and I had been playing together like good friends.

That's right, we were playing hide-and-seek. And then...

"Under the stairs...!"

Leaving everyone in their confusion, I rushed out of the room and headed straight for the space under the stairs.

But where there had definitely been a door that day was now just a plain wooden wall.

"Grandma, there used to be a door here, right?!"

I asked my grandmother, who had followed after me, but—

"Nope, there's never been a door in a place like that,"

she answered with a serious look on her face.

"Is your head still scrambled? Go get some rest."

Told so by my mother, I had no choice but to return to the Japanese-style room.

In the end, I fell into a deep sleep until nightfall, during which I had a strange dream.

It was a dream where I was searching for Masaya in that grassy field.

Whenever I called his name, a voice would answer, "I'm over here!" but when I walked toward the voice, nobody was there.

Searching and searching in the oppressive heat like that, I finally spotted Masaya's back.

"Masaya!!"

As I rushed up to him, Masaya slowly turned around.

But Masaya's face was...

"Waaah!!!"

I woke up screaming, and my father, sleeping beside me—

"What's wrong? Did you have a scary dream?"

—asked as he patted my head.

My mother also rubbed my back with a worried look.

Tears streaming down my face, I endlessly—

"Masaya, I'm sorry. Masaya, I'm sorry..."

—muttered over and over.

It was because I couldn't open the door properly that Masaya was trapped in that world.

As soon as summer vacation ended, I returned to Tokyo, but I kept having dreams about Masaya for a while after that.

However, Masaya's figure gradually faded, and eventually, he stopped answering even when I called his name.

Before long, I stopped having dreams of going to the grassy field, my memories of Masaya faded, and I gradually came to think, "Masaya must have just been an imaginary friend."

Many years have passed since then, and my grandparents' house deteriorated to the point where it was decided it would be demolished.

When my family visited my grandparents' house to take one last look at it, I found something lying on the ground in front of the back door.

It was the tiny flashlight that Masaya had been holding on that day.

Ever since then, I haven't set foot anywhere near there.