Chapter 43: The Pseudo-Sister

"Th-Then, everyone! I’ll be heading home for now!"

The pool cleaning was finally finished. After getting completely carried away playing around, night had already fallen.

Asiri had finished explaining the internal structure, they’d eaten dinner together, and everyone had begun preparing to sleep.

"Yes! Thank you so much for everything! And for joining us for dinner too…"

"I-It’s fine… I also, um… had fun!"

"…Yeah. Me too."

"…Hehe, indeed."

"I-I didn’t really…"

Koharu was just about to deny it when—

"K-Koharu-chan…? Don’t tell me you were… bothered by us?"

"Koharu, was that really how you felt?"

"Ah—ugh! Fine! I had fun, okay!? Are you happy now!?"

Koharu was a kind-hearted student by nature.
Faced with Asiri’s teary eyes and Azusa’s sulking face, she had no choice but to give in.

"Hehe—Operation success…"

Of course, at least in Asiri’s case, that “operation” was a deliberate act meant to draw out Koharu’s true feelings.

"Operation success, you say…?"

Koharu opened her mouth to protest such uncharacteristic cunning, but perhaps due to fatigue, she just didn’t have the energy.

"Once again, thank you so much, Asiri. I’ll be counting on you from now on too."

"Y-Yes…"

Asiri felt a little awkward as Sensei addressed her.
To be honest, even from today alone, she could tell—Sensei wasn’t a bad person.

Every action showed genuine concern for the students.
She was always attentive to her surroundings, quick to warn them whenever a situation turned dangerous. Somehow, Asiri could even understand why her best friend had trusted this Sensei.

Maybe it was still too soon to make that kind of judgment.
But while Asiri was naturally cautious, once her guard dropped, she was hopelessly easy to sway—and the fact that she didn’t even realize it herself only made things worse.

Now, she couldn’t help but feel that her attitude up until recently had been terribly rude.

"Ah, also…"

"…?"

Still, putting that aside—

"I went ahead and separated the rooms just in case, so… please, don’t do anything weird, alright!?"

"I won’t!?"

When it came to that kind of trust, though, that was an entirely different matter.

"…?"

Late at night, while Sensei was finishing up some leftover work in his room, three soft knocks sounded at the door.

"Come in."

"Ah, um, excuse me…"

Peeking timidly through the slightly opened door was Ajitani Hifumi, the head of the Supplementary Lessons Club.

"I’m sorry for disturbing you so late…"

Sensei closed his overheated laptop, swiveled his chair around, and faced Hifumi.

"Hifumi? What’s wrong?"

"Um… how should I put it… I just couldn’t sleep, and when I started thinking about things, it kind of… ahh…"

Staying up this late despite having class tomorrow wasn’t ideal—but her anxious expression said everything.

After all, the fate of their Supplementary Lessons Club was still uncertain, and as its president, Hifumi must have felt the weight of responsibility.

Though she had seemed fine during the day, she must have been more troubled than she let on.

Sensei decided it would be best to hear her out.

"I see. In that case, will you keep me company during my break? How about some tea?"

"Ah… thank you so much…"

They began chatting over cups of tea, and little by little, Hifumi started opening up about the real reason she’d come.

That if they failed the third test, they’d be expelled.
That it was because a traitor existed among them.
That Kirifuji Nagisa had asked her to help find that traitor.

Her wording differed slightly, but the contents were nearly identical to what Nagisa had already told Sensei.

In a way, Nagisa had entrusted Hifumi because she trusted her.
But the fact she hadn’t mentioned asking Sensei for help too… probably meant she still doubted Hifumi, at least a little.

Contradictory as it seemed, it was exactly the kind of careful, calculated move someone like Nagisa would make.

"Th-That whole thing about there being a traitor… I just can’t—"

Hifumi’s trembling voice cut through Sensei’s thoughts.

"We’re all students from the same school…! Even today, we cleaned together, played in the pool, cooked dinner, ate together… bit by bit, we were starting to get along…"

Her voice grew heavier, thick with emotion.

"And now they want us to find out who the traitor is… something like that… I just… I can’t…"

Finally, she fell completely silent.

After a short pause, Sensei spoke softly.

"Hifumi, you’re kind, aren’t you?"

"…!? Wh-What!? No, that’s not—"

"You don’t need to worry about that matter, Hifumi."

"S-Sensei…?"

"Leave it to me. I’ll take care of it."

Hifumi could only blink in surprise.
She hadn’t expected those words—not sympathy or comfort, but an offer to shoulder the burden himself.

"Hifumi, I want you to focus on doing what you can do."

"…What I can do."

She paused to think.

"…Okay! I understand! I don’t really know what that is yet, but… I’ll give it some thought!"

"Good. And if you ever need my help, just say the word."

"Thank you! I feel so much lighter now!"

And with that, Ajitani Hifumi’s worries, at least for the moment, were eased—thanks entirely to Sensei’s gentle support.

…Meanwhile, elsewhere—

"Well, well… so that’s what was really going on."

Two eavesdroppers were secretly listening in.

"Honestly, it’s not what we were after, but… what a juicy bit of info, huh?"

"H-Hey… I still don’t think this is right…"

"Oh, please. When have we ever had the luxury of choosing clean methods?"

"Th-That’s true, but still…!"

Maybe it had been a mistake to involve this one after all.

Asiri couldn’t help thinking that as she listened to the voice on the other end of the call.
She had wanted to resolve things more peacefully.

But there was Shirasu Azusa, a student who might be linked to Arius Branch School.
They’d already informed everyone in the group—but of all people, she had chosen this partner.

Thinking about it now, she still couldn’t tell whether this person was a fool or a genius.

More importantly, this was the same person who had once dragged Sensei into their mess without telling anyone—intentionally, at that. A repeat offender with zero remorse.

"Of course, I’ll keep things reasonable, you know? You didn’t install anything in the bathrooms or toilets, right?"

"Th-That’s not okay!! If any of that data ever got leaked or sold, it’d be a total disaster!!"

"What do you take me for, honestly…"

The person on the other end let out a tired-sounding sigh.

"Still, you did well with that matter. Someone connected to the Arius Branch School… Shirasu Azusa, was it?"

"Yeah! Azusa-chan!"

Asiri said the name brightly, almost cheerfully.

Ah, she’s already been won over, I thought before speaking my mind.

"Arius Branch School, huh…? With the signing ceremony coming up, it’s a suspicious time for something like this to appear. Personally, I suspect there’s a spy involved."

"B-but you know!? I talked to her a little, and she’s such a good girl…!"

"I’ve heard that more than a few times now. It’s not that I don’t believe you, but…"

"But…?"

"You’re way too easy to win over."

"Wha—!? I–I’m not easy!!!"

"This is exactly what I mean…"

With an exaggerated sigh, Mayumi leaned back and raised both palms toward the ceiling in mock defeat. Unfortunately, since this was an audio-only transmission, Asiri couldn’t see it.

The real problem was that Asiri herself had no self-awareness.

At this rate, they’d never reach their goal.

"Well, I can’t say I hate that kind of softness, though… Anyway, speaking of which—the girl from Arius is right here. She’s been around for a while now, actually."

"Eh!!? A-Azusa-chan!?"

"The pink-haired, well-endowed one. Asiri, maybe take a few notes from her."

"Hanako-chan—w-wait, that’s totally irrelevant right now!!"

"I’m joking."

"Y-you’re teasing me again, Mayumi-chan!!"

Mayumi chuckled softly, amused by how flustered Asiri was getting even from afar.

Feeling a little bad for teasing her too much, she brought the conversation back on track.

"Now then… I wonder what kind of conversation they’re having?"

"Uu… I’m sorry, everyone…!"

Azusa, who had been fixing her uniform and standing still for some time, was approached by Hanako.

"Oh my, Azusa-chan? You’re still awake? And in your uniform…?"

"I slept a little. So I thought I’d keep watch for a while."

"Keep watch…? But you look rather sleepy, you know? Are you sure you actually slept? Your head’s been nodding this whole time."

"Now that you mention it, that’s true," Mayumi murmured.

Indeed, just as Hanako said, Azusa looked noticeably drowsy.

"…Yeah. The truth is, I didn’t really sleep. I can’t rest well in unfamiliar places."

"…"

"Don’t worry. I can manage staying up all night if I need to."

"Ah, Azusa-chan…!! I—I’m going to go hug her!!"

"Calm down, you fluffy-headed blonde. If you go now, it’ll look like you’re confessing that you’ve been eavesdropping."

"T-that’s too mean!!!"

Suppressing Asiri’s sudden impulse to act, Mayumi redirected her attention to the two’s conversation.

"No… that’s not really what I meant," Hanako continued.

"Are you out for a walk too, Hanako? It seems Hifumi went for a stroll somewhere as well. Everyone’s probably uneasy in a new place, so I thought keeping watch might help. My pseudo-sister used to do the same thing."

"I see…"

"'Pseudo-sister'? What’s that supposed to mean?"

"Oh, maybe it’s that ‘something like a sister’ she mentioned earlier today," Asiri said.

"And what does that even mean?"

"Don’t ask me! I have no idea!"

───Why is she acting like that’s totally normal?

Mayumi thought that to herself but didn’t say it aloud.

"…In that case!"

While they were talking, Hanako slowly sat down beside Azusa.

"Until you get sleepy, would you tell me about her? That person. And maybe a bit about your previous school—just whatever you’re comfortable sharing. Like your friends, for example."

"…"

Azusa blinked, confused by Hanako’s sudden request. Then she realized Hanako was simply trying to put her at ease, and her lips softened into a faint smile.

"…Thank you. Let’s see, my pseudo-sister… it must have been three or four years ago. She suddenly appeared in front of me one day."

"'Pseudo-sister'… could that be a teacher or a student at Arius?"

"Maybe, I guess…? Oh, but you know, she said something like this—"

Asiri relayed to Mayumi what Azusa had told her earlier that day.

"…What the hell? That’s the complete opposite of what we know."

"R-right!? I was wondering about that too…"

"In any case, we’ll need to hear the rest of her story."

"Y-yeah…!"

She paused for a moment, then turned her focus back to the hidden camera feed.

"…At the time, I was… injured because of certain circumstances. She protected me, but I’d already taken a lot of damage. She treated my wounds—and directed her anger at the ones who caused them."

"…She sounds like a kind person."

"Yeah. …But the problem came afterward. Besides me, there were four others she protected… and she treated all of them as her little sisters. Completely one-sidedly."

"One-sidedly… as little sisters?"

Everyone except Azusa wore identical looks of confusion.

To treat someone as a sister without consent—it wasn’t that they didn’t understand the words, but their minds refused to process them.

"That’s right. We weren’t related by blood, and it was the first time I’d met her. Yet she treated me as a sister. Or more precisely—she treated everyone in that school as her sisters."

"U-um, why are you smiling so fondly while saying that? This is supposed to be a nice story, right? Because right now, it sounds more like the setup for a horror story…"

"Exactly."

Mayumi agreed flatly with Hanako’s remark.

At this point, the story sounded less like a heartwarming memory and more like a strange encounter with a mysterious stranger.

"…Anyway, she taught me—and the others—so many things we didn’t know. She protected us. It was all new to me. Her methods were odd, but… when I didn’t understand something, she’d think it through with me. When things were hard, she’d tell me we’d get through it together. She always listened to what I had to say. The same was true for the other four."

"…That’s… really something."

"So I’m grateful. She’s not my sister, but I owe her a lot."

"…Heh. I see. Then—was there any particular story that stuck with you? I’m rather curious now."

"Yeah, of course. Let’s see… that was probably…"

"…Huh. That’s a lot more normal than I expected. I thought it was going to turn into something creepy, but she actually sounds like a good person."

"Uu…! Azusa-chaaaan…!! That’s so sad…!!"

"Alright, alright, calm down. Wipe your tears—come on, deep breaths."

"Fuuu… haaa…"

Mayumi guided Asiri through calming breaths, helping her settle down.

Honestly, Mayumi herself wasn’t exactly the most serious person—but when dealing with Asiri, she had no choice but to play the responsible one.

Otherwise, they’d both end up doomed together.

"But this settles it."

"Sniff… what does?"

"The Arius Branch School’s situation. We’ve got a clue now."

"…?"

"The pseudo-sister. If we can learn more about that irregular presence, we might get a clearer picture of what’s happening inside Arius."

"Ah, r-right!"

If they could figure out the gap between what they knew of the Arius Branch School and what Azusa described—and if that difference stemmed from this so-called pseudo-sister—then they could begin unraveling the mystery of what was really going on there.

That was clearly what Mayumi meant.

"Which means, for now, we still can’t reveal our true identities to Azusa. If anything goes wrong, we’ll be in serious trouble."

"Y-yeah…"

A brief silence followed.

Both of them thought hard about what to do next.

"…I’ve decided."

"Huh?"

Mayumi was the first to reach a conclusion.

"I’ll start preparing something. I’ll explain later, but I’m going to be busy for a while—so if there’s an emergency, contact me through this line instead of MomoTalk."

"Ah, wait—! She hung up…"

What on earth was Mayumi planning?

Asiri wondered that as she turned her gaze back to the hidden camera feed.

"And then, after that…"

Azusa’s voice carried faint joy as she continued talking about what had happened back then.

"Fwaaah… I guess listening any further would just be intruding…"

Watching her through the monitor, Asiri finally powered off the device.

"…That was close."

Inside a restroom in the annex, Azusa exhaled quietly, a small communicator held in her hand.

"I didn’t expect everywhere except here to be bugged… I almost let something slip."

She let out a soft sigh of relief and slipped the device back into her pocket.

"…Not being able to meet in person is a problem. This just got complicated."

Her quiet murmur faded into the predawn darkness—
leaving no one to hear her words.