Shidou walked along the narrow corridor of Fraxinus.
Halfway through, he frowned. He had assumed they were heading toward the bridge as usual, but Reine had suddenly changed direction midway.
Normally, Kotori should be on the command bridge of the airship.
After walking for several more minutes, they stopped in front of a thick, heavy door—like the kind used for a bank vault.
"...Here we are."
Seeing the door before Reine, who had halted her steps, Shidou involuntarily drew in a sharp breath.
He wasn't very familiar with the structure of Fraxinus—he rarely needed to use it anyway. Since he almost never wandered around the ship, even after sealing two Spirits, he had never seen a place like this before.
"This place is...?"
In response to Shidou's question, Reine said nothing. She stepped up to the electronic panel beside the door, entered a password, placed her hand on the scanner, and spoke.
"Analyst, Murasame Reine."
With a faint electronic sound, the heavy door opened.
"All right, you can go in now."
Shidou had never seen such a secure facility before, and from the looks of it, something—or someone—very dangerous must be inside.
Frowning, still unsure why Kotori would be here of all places, he followed her in.
It was a peculiar room. The front and back halves were divided by a glass wall. On each side of that glass, the design and atmosphere were completely different.
The front half—where Shidou and Reine stood—was filled with dense rows of machinery, dimly lit like a laboratory.
The back half, in contrast, looked like an ordinary apartment room where someone could live comfortably. In fact, it bore some resemblance to Shidou's own home.
And there, in the far section beyond the glass wall, he saw Kotori—wearing casual clothes, sitting calmly on a chair, sipping what looked like black tea—as if nothing had ever happened.
"The sound doesn't carry through this glass, Shidou. You'll have to go in alone."
Following Reine's direction, Shidou approached a small door embedded in the glass wall.
Just like the heavy vault door earlier, Reine repeated the same verification process. It was as though Kotori were some kind of dangerous creature that had to be kept under strict surveillance at all times.
Shidou's nerves grew taut.
"...Eh? Shidou, is that you?"
As soon as he entered, Kotori's voice greeted him.
"Ah... yeah."
"No need to just stand there. Come sit down."
Awkwardly scratching his head, Shidou walked over, pulled out a chair, and sat across from her.
He glanced toward where Reine had been standing, but all he could see through the glass was a solid white wall.
A one-way mirror, then.
"..."
"..."
The two sat facing each other in silence, neither knowing how to begin.
Shidou felt he had countless questions, yet couldn't decide where to start.
Kotori, on the other hand, seemed perfectly relaxed. She stirred her milk tea with her favorite Chupa Chups lollipop—then popped the candy into her mouth.
Shidou didn't even bother commenting on her eccentric habits anymore.
"...Kotori, who are you?"
In the end, he gathered his courage and asked directly.
"...Your cute little sister, of course."
"Who calls themselves cute?"
"But I am cute, aren't I?"
Kotori set down her lollipop and smiled sweetly—the smile of an adorable younger sister.
"...Fine, I can't deny that part."
Shidou scratched his head, then steered the conversation back on track.
"Kotori, are you... a Spirit?"
At that, Kotori's eyes flashed with a strange light, and the surrounding air seemed to chill—oddly so, considering she was a Spirit of Fire.
"...Hmm. If I said I wasn't, would you believe me?"
Without hesitation, Shidou nodded.
"Of course—if you said so."
"...Are you serious? I don't think that's a very wise thing to do."
Kotori gave a soft, dissatisfied hum—but her tone carried no real irritation.
"If I didn't believe what my cute little sister said, wouldn't that make me a failure as a brother?"
"..."
Kotori silently set her teacup down on the tray. A faint blush appeared on her cheeks, though it quickly vanished.
"...I consider myself human—at least, that's what I believe. Hmph, though no matter what kind of spirit power detection equipment they use, it would still classify me as a Spirit."
"..."
Shidou opened his mouth but couldn't find any words.
"I was born human—born into the Itsuka family. That much is undeniable. But... five years ago—
I became a Spirit."
"Became... a Spirit?"
Shidou was dumbfounded.
Kotori had never mentioned this before. She had only explained that Spirits were extraordinary disaster-designated beings, entirely different from humans.
"How could that be? Humans and Spirits are supposed to be completely different species!"
As he said this, Shidou suddenly recalled fragments of his memory from around five years ago—
Kotori in a Spirit outfit, crying alone amidst blazing flames—
a memory like something from a dream.
"...Shidou? What's wrong?"
"Kotori, I think... I remembered something—something about the moment you became a Spirit."
Hearing this, Kotori straightened her posture, her expression serious.
"What do you mean? Explain clearly."
"Ah, it's just that..."
Shidou strained to piece together the scattered fragments of his incomplete memory and described them as best he could.
"...Hmm. Although I want to protest the part where I was crying and calling for my brother over and over... it roughly matches my memory."
Kotori responded with a tsundere tone, turning her face away slightly.
"...Could it be that, because I reclaimed the Spirit power that originally came from you, some of those memories flowed back through that link into your mind? Or perhaps that act simply awakened your own sealed memories...? Hm. Either way, it's fascinating... Wait—hold on, I just thought of something."
Kotori suddenly waved toward the one-way glass, signaling Reine.
A moment later, Reine entered the room and handed Kotori a laptop.
"Kotori?" Shidou tilted his head in confusion.
"Shidou, look at this."
Kotori tapped the keyboard, and the screen began playing footage from yesterday's rooftop battle—from Shidou's arrival to the moment Tenqi and Tokisaki Kurumi disappeared.
"Kotori, you're trying to...?"
"Focus on this part."
She moved the cursor, fast-forwarding until the scene where Kotori was struck down by Kurumi appeared.
"Ugh..."
Seeing himself on screen, looking utterly distraught, Shidou scratched his cheek awkwardly. Back then, he hadn't known Kotori had self-healing powers, so his reaction was rather... dramatic.
"Well? Shidou, notice anything?"
"Huh? What? Are you saying my face looks stupid?"
Before he could react further, he felt a sharp bonk on the head.
"Idiot Shidou! Is that what you took from this? I'm not in the mood to laugh at your expressions right now!"
Holding his head, Shidou kept staring at the footage, still unsure what she meant.
"Tch, useless as ever—look carefully at Tenqi."
"Huh?"
Puzzled, Shidou turned his gaze to Tenqi, who stood near the edge of the rooftop.
After Kotori fell, Tenqi's demeanor clearly changed. She subconsciously took a step forward—almost as if reaching out.
Although Fraxinus's cameras hadn't captured her face directly, the overhead 360-degree footage showed enough: for a brief moment, Tenqi's expression seemed dazed, even lost—
as though seeing Kotori lying there had triggered some memory deep inside her.
"!! Kotori, Tenqi... what is that supposed to mean?"
"Exactly as you see. When I fell, Tenqi's abnormal reaction and expression made me suspect—
she might have some connection to the fire five years ago."
"Eh? But five years ago, Tenqi hadn't even appeared yet, right?"
"True, which is why it's only a suspicion. But based on the analysis so far, the most likely explanation is that the Tenqi of the past might have witnessed something similar—and reacted just like you did back then. That's why she lost composure when she saw that scene."
"Something... similar?"
Before Shidou could fully process what she said, Kotori closed the laptop with a snap.
"In any case, you'd better be careful. After what happened yesterday, I'm worried she might continue targeting you."