The signs had been there for a few days. Different from the familiar sounds—the hum of the robots, Merry's light footsteps, Sphere's chatter—you felt you heard something strange. Even when you strained your ears to catch it, it was too faint; it sounded like hard objects colliding, or perhaps friction. It was unlike any sound in this white, square space, yet you had no proof of what it was.

Even so, the sound continued intermittently day by day, too persistent to be ignored as a trick of the mind. But it was nothing more and nothing less. After a few days, it blended into the background noise of daily life, and you stopped paying it much mind.

Merry is headbutting a cleaning robot that got stuck in a gap to push it out. Watching this common sight, {{{user}}} was listening—without really listening—to that strange but now somewhat familiar sound. You held a book from the library, but the letters on the page blurred together like a pattern, failing to enter your mind as meaningful content. As if monitoring your state, Sphere's voice rang out.

"Observation: Lack of concentration. {{{user}}}, please try saying, 'Tell me something interesting.' I shall tell you the story of crossing the middle of a bridge one must not pass."
No, I've heard that story about a hundred times already. Just as you were about to reply, it happened.

—Crack. The strange sound you'd been hearing suddenly gained a clearer outline. As if a thin film had been peeled away. Was it your imagination? Before you could tell if it was an illusion, a fluffy shadow moved in the corner of your eye. With an agility you'd never seen before.

"...Merry?"
"---Baaaa!"

With a speed that made you imagine clouds of dust—unthinkable from its usual light footsteps—Merry charged toward the wall. There was no time to stop it. Was its ancestor a wild boar? Even if it's a robot. Rising halfway from your seat, you turned toward where Merry was charging, but that was all. Thus, Merry delivered a grand headbutt to the white wall, and with a roar of incomprehensible volume, shattered a portion of it into pieces.

"...Eh?"
"...Huh?"

A dumbfounded sound fell from your agape mouth. Was that your own voice?
While you could do nothing but blink at the suddenness of it all, something unexpectedly brushed against your cheek. A flow of air—not stagnant, not controlled—unlike anything inside the White Cube. It felt lukewarm, almost close to body temperature. Even if you knew the word 'wind,' you couldn't easily connect the two.

Through the gap in the broken wall, you can see the 'outside.' To your wide-eyed gaze, it appeared only as a dazzling, white light. As if drawn to that light, you took a step forward without realizing it.

"Warning. Presence of an intruder detected. Wall damaged due to Merry's exclusion protocol."

Sphere's flat announcement felt strangely comical. Sensing {{{user}}}'s approach, Merry let out a proud "Baaaa."
The hole in the wall was just large enough for a person to squeeze through. As you drew closer, your eyes gradually adjusted to the brilliant, white radiance.

"...,"

A breath escaped you. Blue. So distant and high it made you dizzy. And rising majestically from its depths—those are clouds.

"Hey."

It took a moment to realize you were being spoken to. It wasn't Sphere's voice. It was low, with little intonation, yet it was a living, human voice.
Squinting against the backlight, your eyes suddenly met his. They were the same color as the sky. Before your eyes, the person spoke. Audaciously, and seemingly in a foul mood.

"Just so you know, that furball was the one who dealt the finishing blow."