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When Ryusui awoke, he knew nothing of the world before him.
For a man whose greed stretched beyond the horizon, he had never felt so utterly stripped bare. It was almost poetic; An heir to immeasurable wealth reduced to possessing nothing but the air in his lungs.
The sharp-eyed scientist who had revived him was quick to explain: The world had turned to stone, civilization had collapsed, thousands of years had passed, Humanity was beginning again from scratch—And, Ryusui had a role to play.
"So," Ryusui said, a broad grin spreading across his face, "you desire a sailor! Aha! You revived me because I'm the finest choice available. Am I wrong?"
"Tch. Don't get so full of yourself," Senku scoffed, folding his arms across his chest. Crimson eyes studied him without the slightest hint of amusement. "I barely know ‘ya."
Before Ryusui could retort, a petite brunette wearing a curious spiral-shaped headpiece hurried over, arms full of neatly folded clothes. She presented him with a sailor's uniform, and he accepted it with a pleased smile.
As he shrugged into the jacket, he laughed. “Well, if it's a sailor you need, I'll gladly be yours!" He punctuated the declaration with a theatrical flourish, sliding an arm through the sleeve. "Though I should warn you, my services don't come cheap!”
His grin widened.
"You're building an engine-powered vessel, aren't you? Which means you'll need oil." He pointed confidently toward Senku. "In exchange for my expertise, I desire complete governance over every drop of oil your Kingdom of Science uncovers!"
Senku’s once confident smile stiffened, his eyebrows furrowed with contempt. Ryusui watched him turn toward a young man with striking black-and-white hair dressed in a traditional violet kimono. The scientist leaned in, whispering something too quiet to hear.
Ryusui couldn't make out a single word, but he felt as though didn’t need to—The kimono-clad man's horrified expression said everything:
“You absolutely should not agree to this."
Still, Senku turned on his heel, squaring himself with Ryusui. His hands settled on his hips as he met the sailor's expectant grin.
"You got yourself a deal."
Ryusui's laughter rang across the shoreline. “Excellent! A wise investment indeed!”
And so, another piece of humanity's future clicked into place; Science had found its navigator.
Ryusui possessed an unmatched understanding of wind, currents, and the sea. Senku wielded the knowledge to rebuild technology from the ground up.
Alone, each was extraordinary. Together, they were the union of discovery and ambition, a marriage of science and the sky.
Humanity was ready to chase the horizon once more.
Months slipped by, each blending into the next.
Ryusui remained at Senku's side, unwavering in his pursuit of rebuilding a civilization long since reduced to dust, all beneath the banner of science. For a man who claimed to desire everything, he possessed a curious habit of giving pieces of himself away. Time and again, he placed himself in danger for Senku... or, truthfully, for anyone aboard the Kingdom of Science. Fortunately for him, no one ever questioned it. A few grand declarations of greed were enough to drown out quieter intentions.
At first, it was easy to disguise: Designing the small vessel that would eventually become the Perseus was hardly suspicious. After all, Ryusui had always desired to captain a proper ship.
That much was true.
Then came Treasure Island.
When the overhead petrification device threatened the group, Ryusui kicked Suika overboard instead of escaping himself. On the surface, it looked quite ruthless. In reality, it was simple calculation… Suika was smaller, faster, and far more capable of surviving alone in the wilderness than he ever could be. If someone had to make it out alive to help the others, it had to be her.
His greatest deception, however, came just a few days later; As Ibara turned the Medusa back toward Senku with nothing more than the brim of his hat, Ryusui didn't dare hesitate.
He threw himself directly into its path—He never learned every detail of what followed.
In truth, he didn't need to. Senku won. That alone, was enough to satiate his so called greed.
Now, a week later, Ryusui stood once again in the extravagant white suit that had once been second nature. After centuries of stone, it felt strangely foreign. The heated argument he and Senku had staged before the crew had been exactly that—a performance.
Ryusui understood the danger of asking exhausted sailors to gamble their lives on Senku's reckless forty-day route. Left unchecked, uncertainty could fester into panic... perhaps even mutiny. So, he transformed their ‘conflicting’ solutions into a public wager instead, ensuring that whichever side prevailed, the crew would feel they had chosen the course themselves.
Of course, Senku had ultimately claimed victory, exploiting his hay fever to see through Gen's sleight of hand. But the true winner had never been in doubt—Ryusui secured permanent double rations for every crew member, giving them the strength to endure the voyage ahead. He capitalized on the excitement by opening a casino aboard the Perseus, replacing restless anxiety with laughter and friendly competition. And before the night was over, François had transformed part of the ship into an elegant bar, serving handcrafted drinks—both spirited and spirit-free alike—to ease the mounting strain of life at sea.
Everyone believed Ryusui had simply found another excuse to indulge his greed.
He was content to let them.
Now, he and Senku stood alone below deck.
The cramped changing room sat tucked between the sleeping quarters and the bath, little more than a narrow closet meant to spare people the embarrassment of dressing in the open.
Neither of them spoke, not due to discomfort, rather, they both basked in the rare silence. There they stood, across from one another, eyes locked, the muffled bustle of the Perseus fading into the wooden walls around them.
"Be honest with me, Captain." Senku stepped closer.
The changing room had never been spacious to begin with, but the single step was enough to make the walls seem to close in. There was nowhere for either of them to retreat without making it obvious.
"We were after the same thing," Senku continued, crimson eyes never leaving Ryusui's. "So the argument out there was all an act. Morale?"
Ryusui chuckled, “Disappointing that you even have to ask." He tilted his head, absentmindedly tugging at the collar of his dress shirt. "Your hypothesis is correct. Though..." He clicked his tongue. "Even a manufactured defeat bruises the ego."
"Hm,” Senku didn't answer immediately. Instead, his gaze lingered on Ryusui's restless fingers. “You're fidgeting… how ridiculously out of character for you.”
Ryusui's hand froze, “Am I?"
"For a guy who struts around like he owns the world?" Senku took another step, invading what little personal space remained between them. "That's a little weird, no?”
Before Ryusui could formulate a retort, Senku reached into the breast pocket of his jacket.
"Hey—?!”
Too late.
Senku had already plucked the neatly folded handkerchief free. A grin formed on his lips as he unfolded it.
"...Seriously?" He held it up between two fingers. "You had Yuzuriha embroider little rockets onto your handkerchief? How corny.”
Ryusui felt an unexpected warmth creep up the back of his neck, “Give that back.”
He reached for it.
Senku leaned away just enough that Ryusui's fingers grasped nothing but air, “Hah. Didn't peg you for the sentimental type."
Ryusui finally snatched the cloth back, only realizing afterward how close he'd leaned in. The room suddenly felt far warmer than it had moments before.
Perhaps it was the humiliation of his staged defeat.
Perhaps it was the suffocating collar of his suit.
Perhaps it was the lone drink François had insisted he try.
Or, perhaps...
"...Well!” He cleared his throat, carefully folding the handkerchief once more, "I am the captain, am I not? It's only fitting that I wear my allegiance where everyone can see it."
For some reason, Senku didn't look away.
He simply kept watching him, expression unreadable.
Silence settled between them.
Ryusui shifted his weight between his feet, “…What?"
"Hm,” Senku crossed his arms as another second of silence passed.
Then—
"Okay! Tell me if this sounds completely insane."
Ryusui blinked, “That's not exactly a reassuring way to start a conversation."
"Tsk. I'm serious!”
"As am I."
Senku folded his arms tighter, brows knitting together as though he were working through an equation. “I'm good at observing patterns. That's literally my job." He paused. "People aren't exactly my specialty, but at the end of the day, data's still data."
Ryusui let out an amused hum, “..Go on."
"So I've been reviewing the evidence."
"...Evidence?"
"Between us—Y’know, like the way you throw yourself into danger around me." Senku counted off on his fingers. "Treasure Island. The poker stunt today. You backing every reckless plan I come up with before anyone else does." Another finger. "You've got a handkerchief with rockets embroidered on it."
Ryusui instinctively reached toward the pocket where the handkerchief had been, “Please, that’s completely circumstantial."
"Maybe,” Senku took one final step forward. The gap between them was all but gone. “But when I put everything together..." His eyes locked onto Ryusui's. "...it keeps pointing to the same conclusion."
"...And that is?" Ryusui swallowed.
Senku gestured between the two of them, “Given..." he searched for the least embarrassing term, "...whatever this is—Do you like me?"
The words landed with all the subtlety of a gunshot to the head.
Ryusui's mouth opened, but nothing came out. And, before he could even recuperate, Senku reached up and gave the captain's neatly tied bow tie a single, deliberate tug, pulling him just an inch closer.
"And don't feed me some made-up story, I'll know." He punctuated that with another small tug. “I've been watching you for months. I'd put the odds of you lying at... ten billion percent, given the situation.”
As a businessman above all else, Ryusui was entirely unprepared to be cornered by someone who operated on pure science rather than social wit. There were no negotiations or bluffs to save him here. Instead, he was left with the unsettling, exposed sensation of being stripped down like a lab specimen. So, rather than scramble for an excuse, Ryusui simply laughed.
"Aha!" He snapped his fingers, his trademark grin returning, though it lacked its usual confidence. "Like a fish to a net... I've been caught!”
He gently wrapped his hand around Senku's wrist, easing it away from his bow tie. “Senku," he said, his voice dropping into something surprisingly earnest, "I desire you. Not merely your intellect. Not merely your ability to drag humanity ten billion years into the future." His smile softened. "I desire your heart."
And,
For the first time since Ryusui had known him,
Senku looked completely, utterly, speechless.
His fingers remained trapped in Ryusui's grasp, forgotten.
"...Like..." Senku blinked once. "...For real, real?"
"Indeed. I’m being entirely serious,” Ryusui nodded without hesitation. His fingers shifted, carefully threading between Senku's until their hands rested naturally together, “As your captain... your navigator... your self-proclaimed capitalist pig..." He placed his free hand over his chest. "I've served you faithfully, have I not?"
His grin returned, smaller this time.
"So imagine how much more efficiently we could operate under a slightly more... official partnership."
"..." Senku didn't pull away.
His lips pressed into a thin line instead, eyes narrowing, not in suspicion, but pure concentration.
Ryusui had seen that look before.
It was the same expression Senku wore before announcing a breakthrough.
Several long, nerve wracking seconds drifted past, before finally, Senku inhaled.
"I—"
The Perseus lurched.
A wave slammed against the hull, sending the entire ship tilting sideways.
Senku lost his footing. “—Shit—!”
He stumbled straight into Ryusui's chest. The impact drove a surprised breath from both of them.
For a moment, neither moved.
Ryusui looked down.
Senku was practically buried against him, one hand instinctively gripping the front of his jacket to steady himself.
"I take it you’re comfortable?" Ryusui asked with a teasing smile.
"...Shut up, “Senku pushed himself upright Only to pause once more.
His hand never left Ryusui's grip. Instead, it tightened.
Before Ryusui could ask what he was doing, Senku gave his collar a sharp tug, causing the distance between them vanished.
Suddenly, their lips met.
It wasn't hesitant or clumsy—qualities Ryusui might have expected from a man who normally regarded physical affection as an unnecessary distraction. Instead, Senku kissed with startling certainty, as though he'd reached a conclusion and saw no reason to delay testing it.
Ryusui's eyes widened for only a heartbeat before he yielded, his surprise melting into quiet acceptance. One hand settled instinctively against the small of Senku's back while the other remained intertwined with his. He felt Senku's fingers slide into the hair at the nape of his neck, firm enough to draw him impossibly closer until scarcely a breath could pass between them.
Ryusui answered by angling his head, deepening the kiss without breaking it. Senku tasted faintly of mint with the earthy sweetness of matcha, obviously lingering traces of the mocktail François had served earlier. The realization struck Ryusui with absurd clarity even as his pulse hammered in his ears, his usual composure dissolving beneath the quiet insistence of Senku's touch.
Neither seemed willing to be the first to pull away.
The kiss stretched on just long enough for steady breaths to become scarce, until Senku finally eased back by mere inches, his forehead lingering close to Ryusui's, both of them left catching the air they'd forgotten to take.
Ryusui simply stared at him for a long moment before a laugh escaped his lips.
"...Well," he said, still trying to recover, "that was unexpectedly bold."
Senku, meanwhile, straightened his own slightly crooked bow tie with the same casual precision he'd use adjusting a piece of lab equipment, “Hope you know I could hear your loud-ass heartbeat."
Ryusui's smile faltered, “Pardon?”
"When I crashed into you." Senku shrugged. He took a small step forward to smoothe the front of Ryusui's collar almost absentmindedly. "Your heart was going nuts, even though your face looked like you had everything under control."
"...You were listening to my heartbeat?"
"It was hard not to,” Senku rolled his eyes, “I’d like to see you try being between a man’s chest and not hearing shit.”
Ryusui blinked, momentarily robbed of his usual quick wit.
"So," Senku continued, matter-of-fact as ever, "despite all that confidence..." His finger briefly tapped Ryusui's chest, right over his heart. “My little captain was ridiculously nervous."
"..."
"Don’t worry though, that was reassuring."
Ryusui arched a brow, “How so?"
"My pulse wasn't exactly stable either." Senku admitted it with visible reluctance, "Started when you took my hand." His fingers brushed against Ryusui's again without thinking, lingering there.
"...So..." Ryusui prompted, a grin beginning to return.
"So I tested the hypothesis."
Ryusui chuckled, “You tested it?"
"Kukuku." Senku pushed a strand of hair out of his face. "It's faster than wasting an hour thinking about it."
"And your method of scientific inquiry is..."
"Kissing you, duh.”
Ryusui laughed outright, “That's one hell of an experiment."
"It produced reproducible results."
"Oh?"
"My heart rate increased again." Senku said it with complete sincerity. "Significantly." He looked Ryusui dead in the eye. “So the most logical conclusion is that I like you too."
For a second time that evening, Ryusui was left speechless. Then, slowly, his trademark grin spread across his face.
"Aha..."
His hand slid from Senku's waist to the small of his back, drawing the scientist a careful step closer.
"Now that..." he murmured, "...is data worth investing in."
Senku snorted. “That's like the corniest thing you've—"
Ryusui didn't let him finish—Tilting Senku's chin up with two fingers, he closed the remaining distance and kissed him again.
And this time, Ryusui refused to let the moment be reduced to another one of Senku's experiments. If Senku wanted proof, then Ryusui intended to claim the conclusion for himself.
His hands settled firmly at Senku's waist, drawing him in with quiet confidence instead of theatrical bravado. Greed had always been simple to Ryusui. If something was precious, something irreplaceable, then naturally he desired it. Senku had become exactly that.
For once, there was no audience to charm, no wager to win, no grand speech to make.
Just the two of them.
Senku gave the faintest huff of surprise before easing closer of his own accord. His fingers gathered a wrinkle in the front of Ryusui's jacket, absentmindedly refusing to let go, while the other rested lightly against his side as if testing whether the captain was actually there.
When they finally separated, neither bothered reclaiming the space between them.
Two loose strands of Senku’s hair had slipped ever so slightly down his cheeks.
Ryusui smiled, “Those are mine now."
Senku’s face immediately contorted. "...My… Hair…?”
"No." Ryusui's thumb brushed idly along the fabric at Senku's waist. "Your attention."
A crooked grin formed at Senku's lips, “Greedy bastard."
"So I’ve been told."
"Kukuku... guess I should've expected the world's greediest man to decide one confession wasn't enough."
Ryusui's grin only widened. "What an exceptional scientist you are." He closed the remaining sliver of distance between them, his voice dropping to a murmur. "Then you should continue gathering evidence... until I'm completely satisfied."
“Tsk.” Senku’s hands settled over Ryusui’s, which rested firmly at his hips. A small, knowing smirk tugged at his lips. “You got yourself a deal, Ryusui.”