Once past the gate, we assumed the same formation we had used during our training with Genya-san—a triangular wedge with Mika and Saori-chan positioned in the center. Yuji took the point, Hiiragi-san held the left wing, and I covered the right.
The interior of the dungeon was dim, so our first priority was switching on our LED lights to secure a reliable light source. Technically, we could have used magic to create light, but since we were here to mentor the girls, we refrained from using any methods they couldn't replicate themselves.
"As you can see, dungeons are dark, so maintaining your light source is critical. There’s enough ambient light to see by, sort of like a night light, but the difficulty of combat spikes if you can’t see clearly enough to identify things instantly. Also, always carry multiple sources in case one fails. Understand?"
"Got it."
"Yes!"
It was a basic lesson, but teaching the importance of light first was about instilling a mindset of redundancy and accident prevention. Even among rookies who know enough to bring a light, many only bring one.
"Now then, you two. We’re officially inside, so let's unsheath those spears. If you leave the covers on, you won't be able to react to a sudden engagement."
"Okay."
"Right."
Mika, Saori-chan, and Hiiragi-san each removed the sheaths from their spearheads and stowed them in their packs. We’d kept them covered while standing in the entry line to avoid any accidents, but now the tips of their weapons caught the LED beams, glinting sharply.
"First, we'll teach you the proper way to navigate a dungeon while we search for monsters. Pay close attention."
"Okay!"
"Understood!"
With our combat preparations finished, we pushed deeper into the dungeon. Yuji led the way as the primary example, while Hiiragi-san and I provided a running commentary on his movements.
"Listen, you two. Even when walking down a simple corridor like this, you can never neglect your surroundings. If you do, you’ll walk straight into a trap or an ambush," Hiiragi-san cautioned.
"Um, what specifically should we be looking for?" Saori-chan asked, watching Yuji's every move.
"For starters, the blind spots. I’ve been watching your eyes, and your gaze is fixed too much on the center of the path. It’s your first real dive, so it’s understandable, but you need to scan more broadly. If you focus too hard on a single point, you create a tunnel-vision effect where you’re looking but not actually seeing."
"Oh, I see."
Mika and Saori-chan both looked startled, as if they’d just realized they were doing exactly that.
Hiiragi-san gave a small, wry smile at their reaction. "It’s hard to put into practice immediately, but try to stay conscious of it. Once you’ve done it enough times, it’ll become an instinct."
Yes, ma'am!
"Hehe. Work hard at it. Once this becomes second nature, you’ll have taken your first real step past being a rookie explorer."
!
Eager to prove themselves, Mika and Saori-chan immediately began darting their eyes up, down, and side-to-side, scanning the walls with exaggerated intensity.
Hey, now. If you stay that wound up, you'll burn yourselves out mentally before we even run into a monster. Take it easy.
"Hiiragi-san, don't egg them on too much."
"I suppose. But this is a fundamental skill for surviving as an explorer, isn't it?"
"Well, you’re not wrong."
Agreeing with her point, I kept an eye on the two girls as they desperately tried to look everywhere at once.
We continued down the straight corridor with more explanations until we hit a T-junction. Yuji came to a halt just before the corner.
"Yuji-san? Why did you stop so suddenly?"
"Hmm? Just a little something."
Seeing the girls' confused expressions, I decided to turn it into a lesson.
"Pop quiz for you two. Why do you think Yuji stopped here?"
"Uh, why he stopped? Um... because he’s not sure which way to go?" Mika guessed.
"Incorrect. While you might hesitate on a new floor, that’s not why he stopped here....Any ideas, Saori-chan?"
I shook my head at Mika’s answer. We were regulars here; we weren't going to get lost this close to the entrance. Saori-chan looked a bit hesitant as she offered her answer.
"Um... is it because he doesn't know what's waiting around the corner?"
"Correct. Well done. When you're approaching a corner or any area where your vision is obscured, you never just walk out and expose yourself. It’s a vital rule to remember."
"Yes!"
Saori-chan beamed at the praise, while Mika pouted next to her, clearly annoyed that she’d missed the obvious answer.
"But Onii-chan, I get why he stopped, but how are we supposed to see what's ahead then? If it’s too dangerous to even stick your head out, what do we do?"
"Good question. That’s why we use this."
I pulled a specific item from my utility pouch.
"...A mirror?"
"Exactly. A telescopic mirror on an extending handle. You both have one in the gear kits you bought, right?"
"...Ah."
"What do you mean, 'Ah'?"
As I explained the tool, Mika’s face fell, looking like she’d just realized she’d made a major blunder. I glanced at Saori-chan, who was wearing the exact same expression.
"S-Sorry, Onii-chan. I didn't think I'd actually use it, so I left it at home."
"I-I'm sorry. I didn't put mine in my bag either."
"Aah... I see. Well, that’s not ideal."
I scratched the back of my head as they both bowed in apology. This was on me; I should have explained the practical application of every tool before we left.
Sigh.
"Well, it's my fault for not going over the gear properly beforehand. Let's just be careful from now on. I'll lend you mine for today, so watch how Yuji uses his and then you can try."
"Okay."
"Yes."
"Alright, Yuji. Show 'em how it's done."
"You got it."
Yuji pulled out his own mirror and began the demonstration.
"Okay, listen up. Before you even think about the mirror, you start by checking for presence."
"Presence?"
"...As in, signs of life?"
Mika and Saori-chan tilted their heads. It was a vague term for beginners.
"When I say 'check for presence,' for now, I mostly mean 'use your ears.' if you hear something sprinting toward you, you don't stand there faffing about with a mirror. In that case, you back away from the corner immediately and wait to see what comes out."
"Oh, right."
"That makes sense."
They both nodded, looking enlightened. Yuji leaned in toward the corner—but not past it—and gestured for silence while he listened. After about three seconds, he pulled back.
"Alright, it's clear. Nothing sounds like it's approaching."
With that, he began extending the telescopic handle of his mirror.
"Once you've confirmed it's quiet, you move to visual confirmation. You slide the mirror out just a tiny bit into the passage like this."
Yuji held the mirror low, near the floor, poking it just far enough to see around the bend. He tilted it to scan the area for a few seconds before retracting it. He then repeated the process for the other direction.
"Done. Both ways are clear. That's how you do a basic corner check. Alright, your turn. Who's first?"
Yes!
Mika stepped up first, approaching the corner to listen. As she did, Yuji called out to Saori-chan, who was watching from behind.
"Wait, Saori-chan."
"Yes? What is it?"
"Sorry, forgot to mention this. While one person is checking the corner, the other party members need to pull security. The person with the mirror is vulnerable and distracted. When you’re in a party, you have to watch each other's backs."
"Oh, right! Understood."
Saori-chan turned around, putting her back to Mika to watch their rear. She looked surprisingly focused, her eyes scanning the corridor effectively. After about half a minute, Mika finished her check.
"Okay. All good, there's nothing there."
"In both directions?"
"Yep!"
"Good. Saori-chan, you’re up."
"Yes!"
Mika handed over the mirror, offering some encouragement. "It’s actually pretty easy. You've got this, Saori-chan!"
"Thanks! Leave it to me, Mika-chan!"
In the split second their attention was on each other, I saw Yuji’s hand move in a blur. He’d flicked something into the passage ahead of them.
"Alright, give it a go. Ready, Saori-chan?"
"Ready!"
"Good. Mika-chan, watch the perimeter."
"Got it!"
"Start."
At Yuji’s signal, they went into motion. Saori-chan began her check while Mika held security. A few seconds in, Saori-chan let out a small gasp.
"Huh? Wait..."
"Something wrong, Saori-chan?"
"Um... there's something in the corner of the hallway, but it's too dark to tell what it is."
She sounded unsure of herself as she reported her findings to Yuji.
"Something's there, huh? Mika-chan, you said it was clear when you looked just now, right?"
"U-Uh-huh. There was nothing."
"Are you absolutely sure?"
Under Yuji’s questioning, Mika wavered for a second before firming up.
"Yes! I checked every inch. I'm positive there was nothing there when I looked!"
"I see... Sorry for doubting you. But if that's the case..." Yuji trailed off, rubbing his chin thoughtfully. After a moment, he looked back at Saori-chan. "Hey, Saori-chan?"
"Y-Yes!"
"If it’s too dark to see, that means you could identify it if we had more light, right?"
"Y-Yes. I think so..."
"Alright. Let's use this."
Yuji reached into his pack and pulled out a thin, plastic rod.
"What's that?"
"A glow stick. It’s a chemical light. You usually see them at festivals or 100-yen stores. Here."
"Oh... How do I use it?"
"Just snap it to break the internal vial and mix the chemicals. Once it starts glowing, toss it toward the object you're looking at. It should give you enough light to see what you're dealing with."
"Okay. I understand."
"Don't worry, the outer casing is plastic. It won't break just from a toss."
Saori-chan carefully bent the rod until it snapped, shaking it until it emitted a vibrant glow. Once it was fully lit, she tossed it around the corner. She peeked through the mirror again.
"...Huh?"
"What is it, Saori-chan? What do you see?"
"Um, it's..."
"Well? Out with it."
"It's a rolled-up towel! There’s just a towel lying in the hallway!"
Saori-chan reported the result with a look of pure confusion. I had to hide a smirk; I’d seen Yuji throw it.
"No mistake?"
"None! It’s definitely a towel."
"...Good. You both pass."
...Huh?
The girls looked completely baffled.
"Sorry, I was testing you. I threw that towel in when you two were swapping places."
...
"I wanted to see if you were actually being thorough. Mika-chan was confident enough in her previous check to stand by it, and Saori-chan didn't miss the new addition. I’m glad to see you’re both taking the search seriously."
Yuji gave them a bright, almost mischievous grin. The girls let out a collective sigh of relief, their shoulders slumping as the tension left them.
We continued our lesson-filled trek through the dungeon until, finally, the moment arrived. Our LED beams cut through the darkness to reveal a figure standing a few dozen meters ahead.
"...Finally showed up," Yuji muttered quietly.
It was a monster.
"Alright, you two. This is where the dive really starts....Ready?"
...
Mika and Saori-chan didn't answer. They couldn't. They were too busy staring, faces tight with nerves, at the monster waiting for them in the dark.