Chapter Text
The lab at dusk had become your shared sanctuary.
You'd spent countless evenings together like this—Senku leaning over his experiments, you perched on a counter or sitting cross-legged on the floor sorting herbs or labeling glassware, quiet conversation threading between clinking tools and the low hum of the evening insects outside.
Dating him hadn't changed the rhythm of your days so much as it had deepened the spaces between them.
His shoulder brushing yours now lingered a little longer.
His hand on your elbow lasted an extra second.
His gaze held yours before sliding away—not because he was shy, but because if he didn't pace himself, he'd get nothing done for hours.
But one thing still hung unresolved between you.
You haven't had your first kiss.
And for the past few months, while the relationship had grown into something stable and warm, neither of you had crossed that line yet.
You waited.
Senku calculated.
Both of you were—quietly, stubbornly—terrified to make the wrong move.
Until today.
It started with a joke.
Chrome had accidentally cracked a flask. Again.
Senku pinched the bridge of his nose. "Chrome, if you break one more piece of glassware—"
"I KNOW, I KNOW," Chrome wailed, "I'm a menace! I get it!"
Chrome scrambled out of the lab in a rush of panic and clattering footsteps.
You laughed. Quiet but warm.
Senku turned.
The laugh hit him harder than the broken flask had ever hit the floor.
It always did.
He crossed the room to stand beside you, one hand braced casually on the table, close enough that your arms almost touched.
"You think this chaos is funny?" he asked, pretending to be annoyed.
"I think it's normal," you said, nudging him lightly with your shoulder. "And kind of... cute?"
He froze.
Senku Ishigami, unshakeable scientist, froze completely.
You bit back a smile. "I mean it."
His red eyes flicked away, just for a second.
"That's a dangerous thing to say to me," he murmured.
"So you keep telling me," you teased gently. "Months later and still blaming me for your emotions."
He huffed—soft, fond, defeated.
"Someone has to take responsibility," he grumbled.
"And it can't possibly be you?"
"Of course not. I'm far too rational."
You raised both brows.
"You're dating me," you said. "That's not rational."
His mouth twitched. "Rationality is overrated."
That was the moment.
You felt it.
The shift in the air.
The warmth in his voice.
The softness pulling at the edges of his smile.
Senku hadn't moved back.
Not even a millimeter.
His hand brushed your wrist as he reached for a jar—too intentional to be accidental. His fingers lingered for half a breath before he pulled away, clearing his throat.
And your heart climbed into your throat.
He still hadn't kissed you yet. But he wanted to.
You knew that.
You felt it.
You lived in it.
Tonight, though... something about him seemed certain.
Ready.
Senku was meticulous.
Precise.
Controlled.
Except when it came to you.
That was how you knew something was shifting—he was fumbling.
Subtle, but real.
His fingers tapped thoughtfully on the table, though he wasn't calculating anything.
He adjusted equipment that didn't need adjusting.
He glanced toward the door, then toward you, then away again.
You hopped off the counter and stood close enough that your arm brushed his.
He stilled.
You leaned into him gently—not enough to overwhelm, just enough to say:
I'm here. I want this. I want you.
His breath caught.
"Senku," you said softly, "are you okay?"
He cleared his throat. "I'm fine."
You tilted your head. "No. You're doing that thing."
"What thing?" he asked, far too defensive.
"The thing where you pretend you're unaffected, but your shoulders go stiff and your voice drops half an octave and you refuse to look at me for more than two seconds because you're thinking too hard."
Senku stared at you.
Then looked away sharply.
"...You really are dangerous," he muttered.
You stepped closer.
"Stop running calculations," you whispered. "Just tell me."
His jaw clenched.
His hands tightened at his sides.
Then—
He turned toward you, fully.
Not a glance.
Not a flicker.
Full attention.
Full focus.
Full honesty.
His voice came low, quiet, raw.
"I've been wanting to kiss you."
Your breath left your body.
You whispered, "Senku..."
"I've wanted to for weeks," he went on, eyes searching yours. "Months. Every time you touch me. Every time you look at me. Every time you laugh at something I say that isn't even funny."
Your heart thudded.
"You could've," you said, gently teasing, gently hoping. "I wouldn't have stopped you."
Senku's expression softened into something dangerously real.
"I know," he said. "And that's exactly why I didn't want to rush it."
You blinked. "Rush it?"
"I didn't want the first time to be—"
"I doubt there is anything you could do that would make it a bad first kiss Senku."
"You know what I mean."
You smiled.
Yes.
You did.
Senku took a slow step toward you.
Then another.
Until your back brushed the lab counter and his hands braced the edge on either side of you—not trapping you, but grounding himself.
You lifted a hand to his chest, fingers splaying over the warmth beneath his clothes.
He inhaled sharply.
You whispered, "So... what changed tonight?"
His eyes flicked down to your lips and back up, filled with restrained want.
"You," he murmured. "You smiled at me and my brain forgot how to function."
"And that's new?" you teased gently.
"Yes," he said simply. "Today it felt... stronger."
He leaned in by a fraction, his hair brushing your forehead.
"And I'm tired of pretending it doesn't."
Your breath caught.
"Senku," you whispered, "kiss me."
He exhaled shakily.
Not hesitant.
Not afraid.
Overwhelmed.
"Yeah," he murmured. "Okay."
His hand slid from the counter to the small of your back, urging you closer—but slowly, giving you every chance to pull away.
You didn't.
You curled your fingers into the fabric of his tunic.
He leaned his forehead against yours, breath warm against your lips, voice low.
"If we do this..." he whispered, "I'm not going to want to stop."
His honesty made your knees weak.
"I don't want you to stop," you breathed.
And that—
That was the ignition.
Senku closed the last inch between you—slowly, deliberately, gently—pressing his lips to yours with the kind of care that made your heart clench.
The kiss wasn't wild.
Wasn't rushed.
Wasn't tangled in adrenaline like the first time.
It was slow.
Warm. Patient. And certain.
His lips moved against yours with a rare tenderness, as if he wanted to memorize the shape of you. His fingers curled into the curve of your waist, pulling you fully into his body.
You slid your hands up to the back of his neck, into his hair, and Senku made a sound—a quiet, startled exhale—that made your entire chest swell.
He kissed you again, firmer this time, his hand coming up to cradle your jaw with surprising gentleness, thumb brushing your cheek.
You melted into him, kissing him back with equal hunger, equal curiosity, equal emotion.
Minutes passed like seconds.
Eventually, he broke the kiss only because you both needed breath.
You rested your forehead against his, panting softly, your hands still tangled in his hair.
Senku's voice was low, rough, warmed by something he never let the world see.
"That," he murmured, "was worth waiting for."
You smiled breathlessly. "Only worth?"
He scoffed a quiet laugh. "Fine. Exceptional. Life-altering. Statistically significant."
You laughed, soft and intimate, and he leaned in to kiss the sound from your lips again—just a brief press, light and warm.
When he pulled back, his eyes were soft.
Almost vulnerable.
"I don't understand the science behind how you mean so much to me already" he said quietly.
Your breath caught.
You lifted your hands to cup his face gently.
"Well, we can figure it out together."
And Senku kissed you again—slow, certain, steady—like he finally understood the equation he'd been trying to solve.