In Theory [Senku x Reader]

1.4 | His First Lie

You snapped a dry reed into thirds, feeding the segments to the fire one by one, spacing them out evenly.

"Do you think they'll get it?" you asked. "The signal? That we're trying to answer?"

Senku's expression didn't change, but there was a look in his eye, like he was already halfway to solving a problem no one else knew existed.

"If they're smart enough to send a smoke response in the first place, then they're smart enough to recognize a repeated pattern. Controlled emission, not random combustion. It's primitive messaging tech—but it works. Been working since 200 B.C."

Tick.

You raised an eyebrow. "I thought you'd at least cite the Han Dynasty. Didn't they formalize military signal systems with smoke and mirrors?"

"Han refined it," Senku corrected, tone clipped but casual.

You sigh, "Yes, they scaled it into a full signal network. Beacon fires every hundred li—alerts across the empire in less than a day."

Senku throws another reed into the fire, "But the base concept? That's been around since Warring States China. Or earlier."

You huff, "Same thing."

He paused, flicking ash from his sleeve.

"Not bad for people who hadn't even discovered vulcanized rubber yet."

You smiled, a little strained at the edges. "God, you're such a nerd."

Without missing a beat, Senku glanced your way. "Please. You're out here quoting dynastic-era supply chain logistics. Let's not get glass houses involved."

You shrug, humming, pretending not to hear him.

He huffed a breath that might've been a laugh, or maybe just a sigh disguised as one.

And still, despite the historical references, borderline stupid conversations, the weight remained. Like something pressing in on the edges of the scene.

Tick.

Taiju and Yuzuriha were noticeably gone.

You tilted your head toward the sky, sighing softly. "Looks like it's going to rain."

The wind shifted, just slightly. Smoke curled eastward, dragged by invisible hands, drifting with a kind of solemn elegance. It felt like punctuation—a comma in the sky. A pause, not an end.

Behind you, the fire crackled. A steady rhythm. Sharp. Consistent. Almost like ticking.
Like the heartbeat of an old machine still trying to remember how to run.

Then—

Crack.

A sharp sound behind you. Too clean for nature. Too intentional for chance.

Not footsteps. Just presence.

And something cold, sharp, settling on your shoulders.

Senku inhaled slowly, shoulders rising and falling with practiced calm. Not surprised. More like he'd been tracking the approach for several minutes and had finally arrived at its inevitable landing.

The corner of his mouth twitched. Just slightly. A breath that wanted to be a laugh, or maybe a sigh.

He looked, oddly, relieved.

Tick.

The hourglass had emptied.

Still crouched, he didn't turn right away. Instead, he flicked the remaining bundle of reeds in your direction. His movements were still, careful—like shelving a book mid-thought.