At the top floor of Arianrhod, in the room where the Dungeon Core’s brilliance could be observed like a star, Rokuhara was with Eina.

Rokuhara maintained his rough demeanor as always, while Eina looked somewhat uncomfortable.

“Ah, you’ve come. Thank you.”

Seeing the two, the Chairman gestured for them to take a seat. After confirming they were seated, he looked up at the ceiling and spoke.

“Is the debt repayment going well? Seems like quite an unamusing amount this time.”
“No problem. I’ve already paid back half of it.”
“As expected of an S-rank. Impressive.”

The Chairman praised him as though speaking to a promising student.

Perhaps annoyed by the attitude, Rokuhara deliberately snorted.
“Hmph, easy for you to say. So, you’re going to offer me a job that’ll take care of the remaining half, right?”
“You catch on quickly.”
“How many times do you think we’ve done this?”

This was a familiar exchange between Rokuhara and the Chairman. Rokuhara always delivered results in his missions. However, in the process, he often caused considerable chaos.

As a result, he would end up taking on even more dangerous missions, ones closer to the depths of the academy city.

“This time, it’s not too difficult of a task… Perhaps even boring for someone like you.”
“After rats, what’s next?”
“The Professor and the Doctor are beginning to move in earnest. It’s likely because the deterrent known as the Professor is no longer around.”
“…Heh.”

For the first time since arriving, Rokuhara smirked.

“I’d like you to keep an eye on them. While we tolerate the activities of The Silver Twilight, we don’t grant them complete freedom. They need to work for the betterment of humanity.”
“Hey, weren’t you all buddy-buddy with them?”
“When it comes to saving the world, yes, we’re comrades. But my interpretation of salvation differs from theirs. Thus, we’re adversaries at the same time.”

The Chairman extended a hand as if trying to grasp the brilliance of the Dungeon Core.

“If the time comes, I’d like you to kill them.”
“Are you sure I’m the right choice?”
“Of course. You have a fundamentally good nature. Ryuuko-kun can’t handle killing, and Tatari-kun is mentally unstable. For various other reasons, I decided on you and Yukihira-kun.”

The Chairman glanced at Rokuhara.
“Given that you’ve killed a lecturer in the past, I think you’re the most suitable.”
“…Tch.”

At the mention of the word lecturer, Eina flinched.

The trembling and dark emotions that welled up from deep within her were a negative legacy etched into her body and soul in the past. Just as she was about to glance at Rokuhara for help, a hand was placed on her head, roughly ruffling her hair.

And with that, the unpleasant sensations dissipated.

“…Leader.”

Without looking at Eina, Rokuhara continued speaking to the Chairman.

“That scum deserved to die. Honestly, I haven’t forgiven you guys for giving him the title of lecturer.”
“That was my failing. Especially with Eina… I caused her pain.”
“No, it’s… fine.”

Eina unconsciously clutched Rokuhara’s clothing as if recalling something. Seeing this, Rokuhara silently turned his gaze back to the Chairman.

“Will you do it?”
“The debt gets wiped clean, right? No reason to refuse.”
“Thank you, Rokuhara-kun. Oh, and while I mentioned both the Professor and the Doctor, your primary focus should be on the Professor.”
“Yeah, he’s the more troublesome one.”
“That’s true, but…”

The Chairman trailed off, hinting at something before continuing.

“The truth is, we don’t currently know who the Doctor is.”
“Seriously? You’ve already lost sight of them?”
“Indeed. The Doctor is extraordinary. Her unique interpretation of the Reincarnation System is awe-inspiring. To think she could repurpose it into a system enabling simultaneous existence…”

Rokuhara mentally retorted, This isn’t the time to be impressed.

“Due to her unique nature, she’s both universal and yet nowhere to be found. At times, there are as many as ten of her existing simultaneously. If you’re going to act, aim for her superior—the Professor.”
“Well, having a clear boss makes things easier for me. By the way, does the Doctor’s location stay consistent?”

The Chairman silently nodded.

“Yes—at the Zilnius Academy.”

■

The beautiful assistant solving the ghost mystery! I’ll do my best!

『Looking forward to it!』

Clearly a spin-off storyline, but there was no helping it.

To prepare for Miyume-chan’s arrival, ensuring the storylines were properly set was the way to go.

I’ll be waiting anytime, Miyume-chan!

And so—

“Welcome to the laboratory of the great genius Kanon-sama!”

We had arrived at Kanon-chan’s lab.

Since the ghost incident would occur at night, we had time to kill here until then.

This is the lab of a beautiful girl, huh? My excitement was rising.

“Miroku-chan already gave permission for us to stay over.”
“Thanks for letting her know, Toa-chan.”

Toa-chan had informed Miroku-senpai that we’d be staying at Zilnius Academy, and judging by her reaction, it went smoothly.

Good, good.

But this lab…

“It’s clean.”
“Yeah, it’s so tidy…!”

Having just come from a futuristic garbage dump-like place, entering such an organized space was surprising.

I thought messy rooms were the default for Zilnius Academy.

“Wait, what’s with your reactions? Did you think I was as bad at cleaning as Luka!?”
“…No, of course not. Right?”
“Y-Yeah, haha.”
“You two are terrible liars!”

How did she know!? My poker face failed!

『Your eyes were darting everywhere.』

Ugh, really?

“Come on, have a seat over here. I’ll make some coffee. Do you want sugar?”
“One, please.”
“I’ll have mine black.”

A mysterious beauty drinking sugary coffee? No way! Black coffee or tea is the way!

“Alright, leave it to me! Making coffee is all about the right temperature!”

With that, Kanon-chan disappeared into the back of the lab.

We sat on the white sofa.

What a neat room. It didn’t feel like the sister of Miyume-chan lived here.

The place felt more like a hospital room, with a small garden viewable outside the window and the scent of disinfectant alcohol lingering in the air.

It was like a hospital waiting room.

“Here you go!”

After about ten minutes, Kanon-chan returned, holding two steaming mugs.

“So, you’re Miyume-chan’s friends, right? I’d love to hear all about her!”

Placing the mugs on the glass table, Kanon-chan’s eyes sparkled as she spoke.

This was totally the kind of move a parent makes when meeting their kid’s friends.

“Even though we’re friends, we’ve only just met, so there’s not much I can talk about, you know?”

“That’s fine! Actually, that’s perfect. She’s the first friend that kid has made in the outside world. Isn’t that fascinating? There’s nothing more interesting than this, right?”

It seemed I didn’t have the option to refuse.
Well, not that I planned on declining in the first place.

“Isn’t Miyume-chan such a good girl? She might lean a bit too much into her thirst for knowledge, but that’s just another adorable, human-like quality, don’t you think?”

“Y-Yes, that’s true.”

Ah, wait. No, this was different. I’d just been dragged into a little sister brag session.

Before I realized it, Kanon-chan’s tongue was in full swing.

“At the Zilnius Academy, she’s been surrounded by similar friends, but I felt like there was something Miyume-chan was missing. Oh, oh! Did you know this is the first time Miyume-chan has ever made a Dive Gear for someone?”

“That’s such a wonderful thing, isn’t it?” Kanon-chan continued.

She seemed genuinely happy that her little sister had chosen to do this herself.

“By the way, who’s the Dive Gear for? Is it for Kei-kun? Don’t tell me he’s already started making moves on her…?! Wow, bold!”

“Ah, no. It’s actually for our senior. Have you heard of Terukami Mizuhi?”

At my words, Kanon-chan tilted her head apologetically.
She seemed utterly uninterested in things that didn’t catch her attention.

Even though someone becoming an S-rank should’ve been noteworthy, Kanon-chan appeared clueless about it.

“She recently became an S-rank. And since she doesn’t have Dive Gear for S-rank use yet, Miyume-chan’s going to make it for her.”

“…Miyume-chan’s making Dive Gear for an S-rank?”

“Y-Yes.”

A brief silence hung in the air.

“…That’s strange. She shouldn’t be able to make something like that yet.”

For just a moment—a fleeting moment—I thought I saw Kanon-chan’s face go expressionless.

It was as if her expression had been forcibly overwritten, but by the time I focused, her smile had returned, bright and cheerful.

“Nameless gave her the materials, or so she said,” Toa-chan muttered hesitantly, avoiding eye contact.

Kanon-chan looked at Toa-chan for a few seconds before suddenly exclaiming, “Ah, I see!”

“So it’s that outsider Miyume-chan mentioned meeting… Hah, honestly, what a busybody. Tampering with someone’s brain directly, what would they do if Miyume-chan broke because of them?”

“Eek!”

Toa-chan let out a startled squeak at Kanon-chan’s sudden shift in tone.

Noticing this, Kanon-chan quickly snapped out of it, her expression awkward as she smiled apologetically.

“Ah, haha… Sorry. Did I scare you? Luka even calls me a siscon sometimes. When it comes to Miyume-chan, I guess I get a little carried away.”

Hmm, so Zilnius Academy really is just full of eccentrics, huh?

Still, if it’s a sister who adores her sibling, well, that’s a beautiful girl worth respecting endlessly.

This is the brilliance of someone with the older sister attribute…!

“You really love Miyume-chan, don’t you?”

“Of course. We’re the only family each other has. Our parents died when we were little, so Miyume-chan is my precious little sister.”

Kanon-chan said this with a smile.

She dropped several spoonfuls of sugar into her mug, stirring it with a stick at a precise, mechanical speed.

The oddly robotic motion drew my attention.

“She’s my family, someone I promised to always be with. I want her to grow up properly.”

Kanon-chan’s gaze softened, as though Miyume-chan were right in front of her.

“—I’m really glad she made a friend.”

Her words, brimming with sisterly love and familial devotion, were ordinary enough.

But.

“—!?”

“Huh? Kei-kun, why did you suddenly stand up?”

Before I knew it, I had risen to my feet.
No, more accurately, my body had moved instinctively in defense.

‘What’s wrong?’

“Uh, I-I just thought I’d head to the restroom.”

“Oh, it’s at the back of the lab, turn left,” Kanon-chan replied casually.

“Thank you.”

I walked toward the lab’s restroom.

『Partner, what happened?』

Could I have been mistaken?

For a split second, it felt as if Kanon-chan’s radiance as a beautiful girl had vanished entirely.