I was Thrown into an Unfamiliar Manga

The Seven Mysteries of the Academy that Satoru told me about over the phone were as follows:
1. The Fox Stairs
2. The Girl Ghost of the Music Room

3. The Radio in the Broadcasting Room
4. The Human Specimen in the Nurse’s Office
5. Hanako-san of the Toilet

6. The White Face in the Window
Aside from the last one, they were all the kind of urban legends I’d heard somewhere before.
“Wait, if it’s the Seven Mysteries, why are there only six?”

[Ah, that. Apparently, anyone who experiences all six legends dies. That’s the seventh one.]
“……”
That’s scary in its own way.

I felt a chill and rubbed my arms.
[More importantly, shouldn’t you have reached the classroom by now? What’s taking so long?]
“That’s because you suddenly started telling me creepy stories. If we weren’t on the phone, I would’ve been there ages ago.”

Grumbling, I placed my hand on the door of Class 2-B, where I’d just arrived.
Clunk!
“Ah.”

Come to think of it, all classroom doors are locked after school to prevent theft.
The fact that I’d only just now remembered that simple truth… I guess my forgetfulness was acting up.
‘Now what?’
The classroom keys were in the second-year faculty office.

I’d have liked to sneak in and grab them, but that place had proper security installed—any attempt would definitely set off an alarm.
As I stood there, debating whether I should just give up on the Japanese ✧ NоvеIight ✧ (Original source) textbook and go home, my gaze happened to fall on the window down the hallway.
The latch was open.

The person on class duty today must’ve forgotten to check it before leaving.
For me, it was practically a stroke of luck. I slid the window open and reached inside.
Click.

Soon, the lock gave way, and the door to 2-B opened.
I carefully stepped inside.
“……”

The classroom was silent.
Since my seat was in the very back, it was right in front of me the moment I opened the door.
I bent over and rummaged through my desk drawer.

“Ah, there it is.”
Luckily, the Japanese textbook I was looking for was safely inside.
Now that I’d achieved what I came here for, I slipped it into my backpack, locked the door from the inside, and stepped back into the hallway.

‘Time to head home.’
Just as I turned around with that thought—
Flash!

A bright light suddenly shone straight at me, and at the same time, a small figure let out a shrill, ripping scream.
“Kyaaaaaaaaaaaaaaa!!”
It was like the cry of a pterodactyl—so loud it echoed throughout the entire school.

My instincts kicked in, and I immediately realized I was screwed. I lunged forward and clamped my palm over the mouth of the screamer.
***
Mizuki Nanae, the assistant homeroom teacher of Class 2-B, was pulling night duty in place of another married teacher with only a few days left before finals.

Technically, her shift was supposed to be next week, but that teacher had used a sudden excuse about feeling sick due to her period and left early, so the youngest in the office—Mizuki—got stuck covering.
It wasn’t her first time doing night duty in a dark, unlit school, but she still hadn’t gotten used to it.
Most people probably didn’t realize that a place so lively during the day could turn this cold and lifeless at night.

「No, no, no, you can’t react like that there! Naocchi! Be more pure-hearted!」
「Like this?」
「Wahahahahaha!」
Sitting under the kotatsu in the faculty lounge, watching a late-night variety show with actors and idols on her smartphone, Mizuki was thinking just that.
But right then—

Step, step!
“Huh?”
The sudden sound of footsteps outside made her whip around in shock.

“……”
It was currently 9:30 PM.
It wasn’t yet time for the security guard’s usual rounds.

But she’d definitely just heard footsteps.
Normally, she would’ve written it off as her imagination and stayed in the lounge.
But it was exam week.

And there was a very real concern that someone might try to break into the faculty office to steal the freshly finalized test papers—so she had to be extra careful.
In the end, she had no choice. She picked up her flashlight and stepped into the pitch-dark hallway.
Unlike the brightly lit faculty lounge, the classroom wing was filled with dead silence.

The long hallway got darker and darker as you went, naturally triggering the imagination.
What could be lurking in that darkness?
She felt goosebumps starting to rise, so she gave a little shiver and headed toward the second-year faculty office.

“…Phew.”
Thankfully, there were no signs of forced entry.
She checked the padlock on the door again, then swept her flashlight around the area.

The mysterious footsteps she’d heard…
It clearly hadn’t been the security guard.
If it had been, she would’ve definitely heard the jingle of his keys.

Still, Mizuki didn’t have the guts to go wandering alone through a dark school any further, so she decided to return to the lounge.
No point sticking around just to scare herself.
But just as she turned toward the hallway leading past Class 2-B—

She froze.
A massive shadow suddenly emerged from the classroom.
It was a figure so tall it almost touched the ceiling.

A towering, musclebound frame.
A hat pulled low over his face.
No matter how you looked at it, it was a suspicious person—and they had just jumped out right in front of her.

In truth, people are scarier than ghosts.
Especially in a place like a school at night, with no one around to help—when you run into a stranger face-to-face, it’s the worst possible situation.
In that moment, the only thing she could do was scream—hoping the security guard somewhere might hear it.

“Kyaaaaaaaaaaaaaaa!!”
It was a calculated scream, born from desperation.
But the man in front of her clamped his thick palm over her mouth in an instant, and Mizuki was on the verge of passing out from fear.

Then, a familiar voice came from the “intruder.”
“Mizuki-sensei?”
‘That voice…’

Through her blurring vision, she finally saw Kim Yu-seong take off his hat—and passed out in relief.
***
“Ha!”

About ten minutes after fainting in the hallway, Mizuki-sensei finally opened her eyes.
I had carried her in a rush to the lit-up faculty lounge and laid her on the floor—she woke up on her own.
“…Where…”

She glanced around the room, then spotted me sitting next to her and let out a high-pitched shriek.
Well… I couldn’t really blame her.
What do you expect from someone who fainted after bumping into me in the hallway?

I quietly waited for her to calm down.
Eventually, she took a few deep breaths, seeming to settle herself. Then she looked at me and asked,
“S-So, Kim Yu-seong-kun, what are you doing at school at this hour?”

Scratching my head awkwardly at her question, I thought: well, that was the obvious thing to ask first.
A student sneaking into school late at night could hardly be up to anything innocent.
I unzipped my backpack and showed her the Japanese textbook inside.

“Actually, I lent my friend the book during lunch, and only realized later that I left it at school. So I snuck in to retrieve it.”
“You do realize that violates school rules, right?”
“…Yes, ma’am.”

As I rubbed the back of my neck, Mizuki-sensei let out a soft sigh, then placed her hands on her hips and scolded me.
“It’s lucky I was the one on duty tonight. If it had been another teacher, there would’ve been no leniency. I’ll keep what happened tonight a secret, so hurry home. Your parents must be worried.”
“Yes.”

After the lecture, I put the book back into my bag and stood up.
“Excuse me. I’ll see you on Monday.”
“Alright. Take care.”

A bizarre little incident at school in the dead of night.
Still, it seemed like it was all wrapping up smoothly.
Just as I thought that and moved to open the lounge door—

“Sensei? Is something wrong?”
Suddenly, a voice came from just outside the door.
Freeze.

I’d been about to unlock it, but stopped immediately and turned back to Mizuki-sensei.
She quickly gestured: ‘Hide!’
I ducked into a corner of the lounge as she motioned.

While I hid, she spoke through the door to whoever was outside.
“Ah, sorry, security guard-san. I just saw a mouse earlier and got a little startled.”
“Really? I thought something happened to you. That scream echoed through the whole school.”

“Ahaha…”
She tried to laugh it off awkwardly, but the guard said,
“Sensei, if you’re alright, could you open the door for a second? I’d like to talk face to face.”

She scrambled for an excuse.
“Ah! C-Can we do that a little later?! I’m changing clothes right now!”
“And… how long would that take?”

“Thirty minutes! Thirty minutes is enough!”
The security guard went silent for a moment—then finally said he’d come back in 30 minutes and left.
Step, step, step, step…

The footsteps gradually faded down the hallway, and I let out a huge sigh of relief from my corner of the room.
“That was close…”
At least we got through it without getting caught, right?

Thinking that, I turned to thank Mizuki-sensei once more.
“……”
But she looked strangely pale.

When I asked what was wrong, she spoke in a terrified voice:
“I didn’t hear the sound of his keys…”