Chapter Text
The call to the Perseus lab wasn’t unusual. Senku was always dragging people in to test his latest experiments, and you’d gotten your fair share of requests. But something about the way he’d asked today had you on edge. Maybe it was the glint in his eye, or the way his lips had curved just a little too knowingly.
You stood at the doorway now, watching him move around the cluttered space with ease, his fingers deftly navigating beakers and glass tubes that gurgled with mysterious liquids. The air was heavy with the scent of herbs and chemicals, sharp and strangely sweet.
Senku didn’t look up when he spoke, his voice casual but carrying that unmistakable authority. “I need your help with something.”
You leaned against the doorframe, crossing your arms. “Why do I get the feeling I’m going to regret this?”
That earned you a chuckle. He finally turned to face you, one eyebrow arched in amusement. His lab coat hung open, sleeves rolled up to his elbows, exposing the lean muscles of his forearms. There was a smudge of charcoal on his cheekbone, just below the scar that split his eyebrow.
“Don’t be so dramatic,” he said, a playful lilt in his voice. “It’s perfectly safe. Probably.”
You narrowed your eyes. “You’re really selling this.”
He grinned, sharp and confident. “I need a test subject for something I’ve been working on. Since we’re headed to America, there’s no telling who we’ll run into. I want to be prepared.”
You glanced at the table behind him, where several glass vials sat neatly arranged, their contents gleaming in shades of blue and green. But one stood apart from the others—a small vial of clear liquid, innocuous and unassuming.
Your gaze flicked back to Senku. “What is it?”
“There’s no telling who we’ll run into in America,” he began, his voice taking on that calculated, matter-of-fact tone that always made you feel like you were two steps behind. “If we encounter hostile forces, we’ll need an advantage. Something to make them talk. This is a truth agent—if it works.”
You raised an eyebrow. “You made a truth serum?”
“That’s the idea,” he said, his tone deceptively casual. “But I need to know if it works on humans. And you,” he added, pointing at you with a slender finger, “are the perfect candidate.”
Your mouth opened, then closed again as you processed his words. “You want me to drink that?”
He didn’t even hesitate. “Yep.”
You took a step closer, arms still crossed protectively over your chest. “And you’re sure it’s safe?”
His eyes gleamed with excitement. “Absolutely.”
“Senku.”
He shrugged, his voice infuriatingly nonchalant. “Probably.”
You huffed, your eyes narrowing. But he was looking at you so expectantly, his posture relaxed yet poised, like he already knew you were going to say yes. Like he always knew.
Your gaze drifted back to the vial. Clear, odorless, harmless-looking. But then again, so were a lot of the things Senku cooked up before they exploded.
You looked back at him, meeting his golden eyes head-on. “If this kills me—”
“I’ll give you a proper burial,” he interrupted, his grin widening. “Scout’s honor.”
You rolled your eyes, trying to ignore the flutter in your chest that always seemed to appear when he looked at you like that. Like you were a puzzle he was eager to solve.
After a long, lingering pause, you let out a defeated sigh. “Fine. But if this backfires, I’m haunting you.”
His eyes softened, just for a moment, before he tossed you the vial. “Deal.”
The glass was cool and smooth in your hand. You hesitated, feeling the weight of his gaze on you, unblinking and expectant. It felt like he was watching more than just the experiment—like he was studying you, dissecting every flicker of hesitation, every shallow breath.
Your pulse quickened, but you forced yourself to keep your expression neutral. No way were you letting him see how easily he could fluster you.
Bracing yourself, you uncorked the vial and tilted your head back, letting the liquid slide down your throat in one swift motion. It was surprisingly cool, with a faintly bitter aftertaste that lingered on your tongue.
For a moment, nothing happened. You blinked, looking back at him with a shrug. “I don’t feel anyth—”
“Who’s the most annoying person on this ship?” he cut in, his voice sharp and sudden.
You opened your mouth, fully intending to say no one. But what came out was, “Gen.”
Your eyes went wide. “I mean—”
Senku’s grin was downright wicked. “Why?”
Your mouth moved on its own, words spilling out before you could even think to stop them. “He keeps stealing my snacks and his stupid pig-Latin drives me insane.”
Your hands flew to your mouth, eyes widening as you looked at him in horror. “What the hell?”
Senku’s laugh was low and triumphant, his eyes gleaming with excitement. “Looks like it works.”
You could only stare at him, heart pounding as the truth sank in. It worked. Which meant…
You were at his mercy.
Your pulse raced as Senku leaned back against the table, arms crossed and eyes alight with intrigue. He was studying you, his gaze piercing and unrelenting, like you were the most interesting experiment he’d ever conducted.
You swallowed hard, your throat suddenly dry. “You… you tricked me.”
He shrugged, entirely unapologetic. “I said I needed to test its effectiveness. And now we know it works.” His lips curved into a smirk. “Beautifully.”
Your cheeks burned. “I thought this was supposed to be for interrogations.”
“It is,” he said, his voice maddeningly even. “But to know how well it’ll work on an enemy, I need to see how it affects someone I already know.” He tilted his head, his hair catching the light, messy and impossibly perfect. “Besides, I had to make sure it was safe first. Can’t go using untested chemicals on strangers, right?”
You scowled, hands dropping to your sides as your fingers curled into fists. “You are the worst.”
His grin only widened. “And yet, here you are.”
You wanted to yell, to stomp out of the lab and slam the door behind you. But your feet stayed rooted to the floor, your body betraying you as his eyes flicked down to your clenched fists and back up to your face, a knowing look in his gaze.
He took a step closer, his movements measured, calculated. “Tell me something,” he said, his voice softening just a fraction. “Why’d you agree to this?”
The truth bubbled up before you could stop it, forcing its way out in a breathless whisper. “Because… you asked me to.”
You slapped your hand over your mouth, eyes wide in horror.
Senku’s eyes widened too, his posture straightening as he looked at you—really looked at you. For once, the smirk was gone, replaced by something almost… curious. Almost vulnerable.
He took another step closer, his voice dropping low. “Is that the only reason?”
Your heart pounded so loudly you were sure he could hear it. You fought against the truth with everything you had, your body trembling with the effort. But the serum was stronger than your resolve.
“…No,” you muttered, your voice barely more than a breath.
His eyes flicked over your face, searching, probing. “Then why?”
You squeezed your eyes shut, willing yourself to stop, to bite your tongue, to do anything other than speak. But the words tumbled out anyway, raw and unfiltered. “Because… I wanted to spend time with you.”
The air between you was suddenly too thick, too heavy. You could feel the heat rising in your cheeks, mortification searing through you. You opened your eyes, fully expecting to see him laughing, teasing you like he always did.
But he wasn’t. He was just… staring. His expression was unreadable, a mixture of surprise and something else you couldn’t quite place.
His lips parted, a breath catching before he spoke, his voice low and careful. “…You did?”
Your throat tightened. “I didn’t… I didn’t mean to say that.”
His eyes softened, the sharpness of his gaze melting into something almost gentle. “I know.”
You turned your head, unable to meet his eyes any longer. Your chest felt tight, like you were standing on the edge of a cliff, teetering on the brink of something you couldn’t take back.
Senku took a step back, his expression shifting as he seemed to remember himself, his usual cool demeanor sliding back into place like armor. “Well,” he said, his tone light, almost teasing. “This is… unexpected.”
You finally managed to look at him, your eyes narrowing. “Are you done playing mad scientist yet?”
His lips quirked up, but there was a softness to his smile this time. “Not quite. Just a few more questions.”
You glared at him. “You can’t be serious.”
His eyes sparkled with mischief. “Completely serious. Science waits for no one.” He leaned back against the table, crossing his arms as he regarded you, his posture deceptively relaxed. “So… who’s the most attractive person on this ship?”
Your stomach dropped, panic clawing at your throat. You tried to bite down on your tongue, to stop the answer before it could escape. But the serum was relentless, forcing the truth out in a broken whisper.
“You.”
The word hung in the air, a fragile, dangerous thing.
Senku’s eyes widened, his confident facade cracking just enough for you to catch a glimpse of the boy beneath—caught off-guard, unsure, maybe even a little stunned.
For a long, agonizing moment, neither of you moved. Neither of you spoke. The silence stretched out, heavy and taut, threatening to snap.
Then, just as quickly, his expression shifted, a smirk pulling at his lips. “Well, well. I should’ve made this serum sooner.”
You wanted to kill him.
But even more than that, you wanted to wipe that smug look off his face.
And if the heat in his gaze was anything to go by, you weren’t the only one feeling the tension between you.
Senku’s grin widened, his eyes gleaming with mischief as he took a step closer, his face just a little too smug. “Aw,” he drawled, tilting his head, his messy hair falling to the side. “You like me.”
Your heart skipped a beat, your pulse roaring in your ears. It wasn’t just his words—it was the way he said them, soft and teasing, his voice dipping lower than usual. It sent a shiver down your spine, one you tried desperately to ignore.
And before you could even think to stop yourself, the word slipped out, too quick, too honest.
“Yes.”
Your breath hitched, your eyes going wide as you realized what you’d just said. You slapped both hands over your mouth, horrified.
Senku’s smirk faltered, his eyes widening just slightly before a new expression took over—something softer, something almost… stunned. He blinked, his mouth opening, then closing again, seemingly at a loss for words.
You didn’t wait to see what he’d say next. Your fight-or-flight response kicked in, and flight won by a landslide. Your body moved before your brain caught up, your feet spinning you toward the door. “I… I have to go.”
You bolted, heart racing, barely hearing Senku call after you. “Hey—wait!”
You didn’t wait. You didn’t dare. Not when your face was on fire, your chest so tight you could barely breathe. You fled the lab, the echo of his voice chasing you down the hall, teasing and lingering and far too dangerous.
You didn’t stop running until you were out on the deck, the salty sea breeze whipping at your face, cooling the heat in your cheeks as you leaned over the railing, gasping for air.
You squeezed your eyes shut, the weight of what you’d just admitted crashing down on you. You liked him. Out loud. To his face. And worse than that—he knew it.
You groaned, burying your face in your hands. “I am never going back in that lab again.”
Meanwhile, back in the lab, Senku stood frozen, his eyes fixed on the spot where you’d stood just moments before. The echo of your voice played over and over in his mind, soft and shy and devastatingly sincere.
“Yes.”
He swallowed hard, his heart thudding in his chest. A slow, disbelieving smile spread across his face as he leaned back against the table, his fingers brushing absently against the empty vial you’d left behind.
“Well,” he murmured, his voice just a little shaky. “Didn’t see that coming.”
But even as he said it, he felt a warmth spreading through his chest, a giddy sort of fluttering that made it hard to breathe.
Maybe this experiment had been more successful than he’d anticipated.