It was the Saturday of the week when I was invited to Nina-chan's house.
I was riding in the car my father was driving, heading toward a middle school in the Kanto area.
However, the sun was already setting, and perhaps because it was the weekend, there was quite a bit of traffic on the roads.
"Hmm. So, this Nina girl has been teaching you magic?"
"Yeah. Nina-chan is really kind, so she's been teaching me a lot of things."
"I see, and that's why..."
As the light turned red, the car gradually slowed down.
"That's why you haven't been practicing magic with me lately, isn't it..."
"No, that's not it! I haven't been practicing with you because you haven't been home, not because I'm practicing with Nina-chan!"
"Hmm..."
In the car, I was recounting the events of the past week while my father had been away. Despite being gone for a week, my father was just as he always was. Well, people don't usually change in such a short time.
As I pondered this, my father slowly spoke up in the stopped car.
"Itsuki, next time, you should bring Nina-chan to our house."
"Huh? Why?"
"She treated you to tea, didn't she? It's only polite to reciprocate by offering some snacks at our place."
...I see, so that's how it is.
Actually, I had visited Nina-chan's house once more after that first time. If the idea is that since she's been hosting me, it's only fair to invite her over sometimes, that makes sense.
But Nina-chan's house is pretty far from ours. While I practice my magic and enhance my endurance through body reinforcement as I walk home, it's not much of a burden for me. But it might be a different story for Nina-chan.
"But, Dad, Nina-chan's house is really far."
"Then I'll drive her home afterward."
"Okay, I'll ask her next time."
"Good. Having a friend is a good thing, Itsuki. Make sure to cherish that."
"Yeah, I will."
By the way, the reason we were heading to the middle school was to exorcise a monster that had appeared at the school.
Before we started talking about Nina-chan, my father had briefly explained the situation. Apparently, the middle school we were heading to was in the process of demolishing its old building to build a new one due to earthquake safety standards and aging infrastructure.
However, two teachers went missing while preparing for the demolition and cleaning out the old building.
Upon further investigation, it was discovered that there was a classroom in the old building known as the "Unopenable Room." The two teachers went missing after they started cleaning it out.
"But Dad," I began, "Why are we going to the school at night?"
It's the weekend, so couldn't we have gone during the day? I thought, but my father's response was surprisingly straightforward.
"Apparently, the room doesn't open unless it's nighttime."
"...Why is that?"
"Most likely, the 'evil spirit' that inhabits the room is nocturnal. Spirits tend to become more active in the evening and nighttime. It's not unusual."
I recalled that when I went bear hunting with Range-san and Aya-chan in Okutama, we did it at night too.
The principal bowed deeply as he made his plea.
In response, my father simply said, "Understood," in his usual short manner. Seeing this, I also steeled myself. People had gone missing, after all.
If I didn't stay sharp, I could end up being swallowed by the "Unopenable Room" just like them.
No room for complacency. My motto is to strike first and get it done before anything happens.
"I'll guide you to the room. From there, I'll leave it to you, Souichiro-san."
"Very well."
With that, we followed Sato-sensei's lead as he guided us to the old school building.
On the way, he told us various things.
The middle school had two buildings, and while they normally used both, the old one was currently off-limits due to the reconstruction. The students who couldn't fit in the classrooms were having their lessons in prefab buildings.
He also mentioned how the rumors of the missing teachers had caused some students to stop coming to school, and others were daring each other to try entering the "Unopenable Room." All sorts of things like that.
When we entered the old building, wearing our shoes as usual, Sato-sensei switched on a flashlight.
A narrow beam of light cut through the dark, empty school.
...This is creepy.
With no one else around, the sound of our footsteps echoed eerily through the halls.
It's just plain scary.
But neither my father nor Sato-sensei seemed bothered as they headed up the stairs.
I took a deep breath and followed my father's lead. The treasured relic from the Raikou Douji I had brought with me clinked softly against my chest, a comforting presence.
After climbing the flashlight-lit stairs, we reached the second floor. At the end of the hallway, Sato-sensei stopped in front of a door with a plate that read "Science Preparation Room."
"This is it. This is the 'Unopenable Room.'"
Standing before the room that Sato-sensei pointed to, I held my breath. I couldn't help it.
...This is...
Noticing my reaction, my father quickly asked me in a low voice, "What's wrong, Itsuki?"
"Dad, this door is covered in Silveit threads. It might be a trap."
"...Hmm."
It was an obviously unnatural sight.
The door was covered in countless Silveit threads, almost like a broken arm wrapped in a cast.
The sheer number of threads, seemingly warning us not to touch it, gave off an aura of madness that sent shivers down my spine.
"Good catch, Itsuki."
With that, my father extended his own Silveit threads toward the door and slowly slid it open. I gathered magic at my fingertips, ready to unleash a quick-shot at any moment.
Who knows what might come out, an oni or a serpent?
The moment I braced myself, my father's Silveit threads were abruptly severed just before reaching the door, coiling and compressing into a cube that dropped to the ground.
As the door to the "Unopenable Room" fully opened, what greeted us inside was...
"Aaah! You pervert!"
A monster covered in tattoos, standing shirtless with a pose straight out of "The Scream," glaring at us with wide eyes.