#shuna

And in the midst of this meteorological chaos, Rimuru Tempest, the slime who had built this federation from nothing, found himself behaving in increasingly unusual ways.

[Y/n] had first noticed the pattern three days into the heatwave.

She had been in the library— One of her favourite places within the Federation's capital— carefully transcribing a particularly complex water-based spell she'd discovered in an ancient tome. The cool stone walls of the library provided some reprieve from the heat, and the silence allowed her to focus on the intricate magical formulae without distraction.

Her Hair, which she'd taken to wearing loose in her humanoid form, cascaded over her shoulders as she bent over the parchment, Half-Lidded eyes scanning the text with intense concentration. The spell in question was a variation of 'Aqua Blade', but this version seemed to incorporate elements of ice magic that she found fascinating. If she could master it, perhaps she could help cool down some of the more heat-sensitive areas of the federation—

"There you are."

The voice made her pause, her pen hovering over the paper. She looked up to find Rimuru standing in the doorway of the library, his golden eyes fixed on her with an intensity that seemed unusual even for him.

"Rimuru-sama," She acknowledged quietly, setting down her pen with careful precision. "Is something wrong?"

He crossed the room with purpose, his footsteps echoing slightly in the vast space. "Wrong? No, nothing's wrong. I just... needed to see you for a moment."

[Y/n] tilted her head slightly, observing him with those perceptive Eyes that seemed to see more than most. He looked flushed— or at least, as flushed as a slime in humanoid form could look. There was something in his expression that she couldn't quite read, a sort of desperate determination that seemed out of character.

"You seem overheated," She noted softly, rising from her seat. "Perhaps you should rest in one of the cooler chambers—"

Her suggestion was cut off as Rimuru closed the distance between them, his hands gently grasping her shoulders. Before she could finish her thought, his lips were on hers, cool and insistent. [Y/n]'s eyes widened in surprise, though she didn't pull away. Instead, she allowed herself to sink into the kiss, her own hands coming up to rest lightly against his chest.

The kiss lasted longer than their usual quick pecks— This was deeper, more intense, as though Rimuru was trying to draw something from her. When he finally pulled back, [Y/n] noticed that he looked more composed, less affected by the heat that had been plaguing him moments before.

"Better," He murmured, almost to himself, before seeming to realize what he'd just done. "S-Sorry! I just... I'll let you get back to your studies."

And with that, he was gone, leaving [Y/n] standing there with her fingers touching her lips, trying to process what had just happened.

By the fifth occurrence, [Y/n] had begun to form a hypothesis.

She sat in her personal quarters— A modest room she'd claimed in one of the quieter corners of the Federation— with several books spread out before her. Unlike Rimuru, who had been reincarnated from another world with knowledge of Japanese culture and modern technology, [Y/n] was a naturally evolved slime. She had originated from the harsh, cold mountains far to the north, where temperatures rarely rose above freezing and survival meant adapting to an environment that would kill most creatures.

Her evolution had been different from Rimuru's. While he had gained his power through consumption and the unique skill Great Sage (now Raphael), [Y/n] had evolved through sheer magical accumulation and study. She had spent decades—perhaps even longer; Time became difficult to track when one was functionally immortal—consuming magical knowledge the way other slimes consumed organic matter.

Mimics had been her particular obsession. Those dangerous dungeon pests that disguised themselves as treasure chests, waiting to trap unsuspecting adventurers. To most, they were nuisances to be avoided or destroyed. To [Y/n], they were libraries of accumulated magic, each one containing spells and knowledge from the adventurers and mages who had fallen victim to them over the years.

She had developed a rather unconventional method of learning from them: allowing herself to be consumed, then forcing them to regurgitate her by pushing deeper into their digestive systems or by unleashing offensive magic from within. It was dangerous, certainly, and more than once she'd nearly dissolved before managing to escape, but the magical knowledge she'd gained had been worth the risk.

This dedication to magic had resulted in her accumulating an impressive arsenal of spells and abilities. More importantly for the current situation, her origin in the frozen mountains meant her body temperature naturally ran much cooler than most beings.

She looked down at her hands— Delicate and pale in her humanoid form, but beneath the surface, still fundamentally slime. Her core temperature, she theorized, was likely several degrees below what would be comfortable for someone like Rimuru, who had been human in his previous life and whose body still mimicked human baseline temperatures despite his slime nature.

"Heat transfer," She murmured to herself, her quiet voice barely audible in the empty room. "He's using me as a heat sink."

It made sense, in a strange way. Every time Rimuru sought her out, he seemed flushed and uncomfortable. Every time he kissed her— And it was always kissing, she noted, never just holding hands or a simple embrace— He seemed to calm down, his temperature seemingly regulating itself through the contact.

The intimacy of it all made her cheeks flush slightly, even as her analytical mind continued to work through the mechanics of what was happening. Rimuru was, consciously or unconsciously, using their physical contact to transfer excess heat from his body to hers. And because her body was adapted to cold environments, she could absorb that heat without discomfort, essentially acting as a living cooling system.

A soft knock at her door interrupted her thoughts.

[Y/n] didn't need to ask who it was. She'd begun to recognize the pattern of his visits— roughly every hour or two, like clockwork, whenever the heat became too much for him to bear.

"Come in," She called softly.

Rimuru entered, and she could immediately see the signs: the slight sheen of perspiration on his forehead, the way his breathing was just a touch too quick, the almost desperate look in his golden eyes.

"[Y/n]," He said, and there was that same driven quality to his voice that she'd noticed before. "I need— That is, I was hoping—"

She rose from her seat, understanding what he couldn't quite articulate. "It's alright," She said gently, crossing to him. "I understand."

The relief on his face was palpable as he pulled her close, his lips finding hers with the same desperate intensity as before. [Y/n] wrapped her arms around his neck, allowing him to deepen the kiss, feeling the heat radiating from his body and the way it seemed to flow into her, dispersing harmlessly through her naturally cold form.

When they finally broke apart, she rested her forehead against his, her purple eyes searching his golden ones. "You're using me to regulate your temperature," she stated quietly. It wasn't an accusation, merely an observation.

Rimuru had the grace to look sheepish. "I... yeah. I didn't realize it consciously at first, but Raphael pointed it out. Your body temperature is significantly lower than mine, and when we... when we kiss, the heat transfer is most efficient because of the increased surface contact and—" He paused, realizing he was rambling. "I'm sorry. I should have asked first instead of just... ambushing you every couple of hours."

[Y/n] shook her head slightly, a small smile playing at her lips. "I don't mind. If I can help you endure this heat, I'm happy to do so." Her expression grew more thoughtful. "Though I am curious why kissing specifically. Surely holding hands or an embrace would also facilitate heat transfer?"

Now Rimuru looked distinctly uncomfortable, a faint blush coloring his cheeks that [Y/n] suspected had nothing to do with the temperature. "...Raphael calculated that the mucous membranes of the lips and mouth provide optimal heat transfer due to increased blood flow and moisture content. It's... it's purely practical."

"Purely practical," [Y/n] repeated, and there was the faintest hint of amusement in her usually reserved tone. "I see."

Rimuru coughed, clearly wanting to change the subject. "Anyway, I should let you get back to—what were you working on?"

"Research into Mimics," [Y/n] replied, turning back to her desk where several books lay open. "I've been documenting the different types I've encountered and the unique magical properties each one possessed. I thought it might be useful information for the federation's archives."

Rimuru moved closer, his interest piqued despite his earlier discomfort. He'd always been fascinated by [Y/n]'s unconventional approach to learning magic. "You really have no sense of self-preservation, do you? Most people flee from Mimics. You actively seek them out."

"They're essentially mobile magical libraries," [Y/n] said, her eyes lighting up with genuine enthusiasm— One of the few times her reserved demeanour cracked. "Each one contains the accumulated magic of every victim it's ever consumed. The knowledge alone is worth the risk."

"The risk of being digested," Rimuru pointed out dryly.

"I've never been digested," [Y/n] countered calmly. "Gagged and expelled, certainly. Nearly dissolved a few times. But never fully digested." She said this as though it were a perfectly reasonable distinction to make.

Rimuru couldn't help but laugh, the sound warm and genuine. This was one of the things he loved about [Y/n]— Her quiet, unassuming nature that hid an absolutely reckless curiosity when it came to magic. She would politely excuse herself from confrontations, avoid conflicts whenever possible, but would willingly throw herself into a Mimic's mouth for the chance to learn a new spell.

"You're incredible," He said softly, and meant it.

[Y/n] looked up at him, surprise evident in her expression. Compliments always seemed to catch her off-guard, as though she didn't quite know how to process them. "I'm simply... curious," She said quietly. "Magic is fascinating. The way it bends the rules of reality, the endless variations and combinations... I could study it forever and never run out of new things to learn."

"Which is why you're perfect for the research division," Rimuru agreed. "Though I wish you'd take a partner with you when you go Mimic hunting. Just in case."

"I'll consider it," [Y/n] replied, which they both knew meant she probably wouldn't. She was too used to working alone, too accustomed to her own company after decades in the mountains before she'd encountered Rimuru and his growing federation.

Rimuru checked the time—a habit he'd retained from his previous life—and sighed. "I should get back to work. Paperwork waits for no slime, apparently."

"Will you be alright?" [Y/n] asked, genuine concern in her voice. "Until your next... heat transfer session?"

He grinned at her phrasing. "I'll manage for an hour or so. Though I might come find you again before the day is out."

"I'll be here," [Y/n] assured him. "Or in the library. Or possibly investigating that new dungeon that appeared near the eastern border—I heard rumors of Mimics."

"[Y/n]," Rimuru said warningly.

"I'll take someone with me," She promised, though her tone suggested she was only saying it to placate him.

With a final kiss— Quick this time, but still effective—Rimuru took his leave, and [Y/n] returned to her research, her mind already working through the implications of their heat transfer arrangement and whether there might be a way to enchant something to provide Rimuru with similar cooling relief without requiring her constant presence.

Though, she admitted to herself with a faint blush, she didn't entirely mind the current arrangement.

It happened during what should have been a routine visit.

[Y/n] had been summoned to Rimuru's office to discuss the magical defenses around the federation's borders. There had been reports of increased monster activity to the south, and Rimuru wanted her assessment on whether additional barrier spells would be beneficial or if they should rely on patrol increases instead.

She'd arrived promptly, her arms full of reference materials and her own notes on barrier magic variations. The office was empty when she entered—Rimuru had apparently stepped out for a moment—so she set her materials down on his desk and began organizing them while she waited.

The heat was particularly oppressive today. Even [Y/n], with her naturally lower body temperature, could feel it pressing down like a physical weight. She couldn't imagine how uncomfortable Rimuru must be, given how much the temperature seemed to affect him.

She heard his footsteps in the hallway a moment before the door burst open. Rimuru entered in a rush, closing the door behind him and leaning against it for a moment, his eyes closed. He looked more affected by the heat than she'd ever seen him—his face was flushed, his breathing labored, and there was a slightly desperate quality to the way he moved.

"Rimuru-sama?" [Y/n] took a step toward him, concern evident in her voice. "Are you—"

She didn't get to finish the question. Rimuru's eyes snapped open, focusing on her with an intensity that made her breath catch. In three quick strides he crossed the room, and suddenly [Y/n] found herself being guided backward, away from the desk, toward the open space near the window.

"Sorry," Rimuru muttered, though he didn't sound particularly sorry. "Can't—the heat—need—"

[Y/n] understood, even through his fragmented explanation. She opened her mouth to tell him it was alright, that she was happy to help, but before she could speak, Rimuru was kissing her with more urgency than ever before.

She responded instinctively, her arms coming up to wrap around his neck, her body pressing closer to his to maximize the surface contact for heat transfer. She could feel the warmth radiating from him, could sense how uncomfortable he must be, and she tried to make herself as available as possible, to provide as much cooling relief as she could.

But in their haste, neither of them had been paying attention to their positioning. [Y/n]'s foot caught on the edge of the ornate rug that covered part of Rimuru's office floor. She stumbled backward, and Rimuru, still pressed against her, lost his balance as well.

They went down in a tangle of limbs, [Y/n] landing on her back on the hardwood floor with Rimuru on top of her. The impact knocked the breath from her lungs, and for a moment they both lay there, stunned.

Then Rimuru propped himself up on his elbows, looking down at her with wide eyes. "Are you okay? I'm sorry, I didn't mean—"

"I'm fine," [Y/n] assured him, though her voice came out slightly breathless. The fall had been unexpected, but as a slime, she was more durable than she looked. "Just surprised."

They should have gotten up. It would have been the sensible thing to do—to extract themselves from this compromising position, laugh it off, and continue with their original meeting agenda.

But Rimuru didn't move. Instead, he looked down at her, taking in the sight of her blonde hair spread out across the floor like a golden halo, her purple eyes wide and watching him, her lips slightly parted. And despite the fall, despite the undignified sprawl they'd ended up in, she looked...

Beautiful.

"[Y/n]," He murmured, and there was something different in his voice now. Not just the heat-driven desperation from before, but something softer, more intentional.

She gazed up at him, her analytical mind noting the change in his tone, the shift in his expression. "Yes?" she whispered.

Instead of answering, Rimuru lowered his head and kissed her again. But this kiss was different from the others—slower, deeper, more deliberate. This wasn't just about heat transfer anymore. This was about connection, about the feelings that had been growing between them since she'd first joined his federation, since they'd first discovered what they meant to each other.

[Y/n]'s eyes fluttered closed as she returned the kiss, her fingers threading through his hair, her body relaxing beneath his. The heat, the discomfort, the original purpose of their meeting—all of it faded into the background, becoming irrelevant in the face of this moment.

Rimuru's hand came up to cup her cheek, his thumb brushing gently across her skin as he deepened the kiss. [Y/n] made a soft sound—surprise or pleasure, perhaps both—and Rimuru felt something warm bloom in his chest that had nothing to do with the temperature outside.

They were so lost in each other, so focused on the sensation of lips and breath and heartbeat, that neither of them heard the office door open.

"Rimuru-sama, I've finished the reports you requested and—OH MY!"

Shuna's voice, pitched high with shock, cut through the haze of their kiss like a bucket of ice water. [Y/n]'s eyes flew open, meeting Rimuru's equally startled gaze. For a frozen moment, no one moved.

Then Rimuru scrambled backward, nearly falling over in his haste to get off of [Y/n]. She sat up more gracefully, though her face was flushed a color that rivaled Rimuru's heat-induced redness. Both of them stared at Shuna, who stood in the doorway with her hand over her mouth, papers scattered at her feet where she'd apparently dropped them in shock.

"This isn't— We weren't—" Rimuru stammered, which was perhaps the worst possible way to handle the situation, as it made them look even more guilty.

"...We fell," [Y/n] supplied quietly, her natural inclination toward truthfulness overriding her embarrassment.

"I can see that!" Shuna managed, her voice strangled. Her eyes darted between the two of them, taking in their disheveled appearance, the position they'd been in. "I am so, so sorry for interrupting! I should have knocked! I'll just—I'll leave these reports outside and—please forgive my intrusion!"

She bent quickly to gather the papers she'd dropped, her movements jerky with flustered embarrassment. Before either Rimuru or [Y/n] could say anything else, she had backed out of the room and shut the door firmly behind her.

Silence descended on the office, broken only by the sound of both slimes' somewhat labored breathing.

"Well," Rimuru finally said, running a hand through his hair, "that could have gone better."

[Y/n], still sitting on the floor, looked up at him with an expression of mortification. "She's going to tell everyone, isn't she?"

"Probably not," Rimuru said, though he didn't sound entirely convinced. "Shuna is discreet. Though we should probably..." He trailed off, not entirely sure how to finish that sentence.

[Y/n] nodded slowly, understanding what he meant. They should probably talk about what had just happened—not the interruption, but everything that had led up to it. The kissing that had started as heat management but had clearly become something more. The feelings that had been developing between them that neither had quite acknowledged out loud.

But before they could begin that conversation, there was another knock at the door—much more hesitant this time.

"Rimuru-sama?" Shuna's voice came through the wood, much more composed now. "I apologize again for my intrusion. However, I should inform you that there's an urgent meeting scheduled in ten minutes regarding the southern border monster activity. The council is already gathering."

Duty called, as it always did when you were the leader of a nation.

Rimuru glanced at [Y/n], who had risen to her feet and was attempting to smooth down her hair and clothing, trying to look presentable. "We'll talk later?" he asked quietly.

She nodded, her purple eyes meeting his with an intensity that suggested she had a lot to say when they finally had that conversation. "Later," she agreed.

They straightened themselves as best they could, collected the scattered reference materials, and prepared to face the council meeting—and whatever gossip Shuna might or might not spread—with as much dignity as they could muster.

Though as Rimuru held the door open for [Y/n], allowing her to exit first, he couldn't help but smile slightly at the faint blush still coloring her cheeks. Heat transfer arrangement or not, something had definitely shifted between them today.

And despite the embarrassment of being caught, he found he didn't regret it at all.

The heatwave broke two days later, much to everyone's relief. Temperatures returned to normal, the oppressive weight lifted from the federation, and life resumed its usual comfortable rhythm.

Rimuru no longer needed his hourly cooling sessions with [Y/n], which should have meant their interactions would return to their previous, more formal dynamic.

Should have.

Instead, Rimuru found himself seeking her out anyway—not because of any heat-related desperation, but simply because he wanted to. He'd find excuses to visit her in the library, would request her presence at meetings even when her expertise wasn't strictly necessary, would invite himself along on her (admittedly dangerous) Mimic hunting expeditions despite her protests that she worked better alone.

[Y/n], for her part, seemed to accept this new normal with her characteristic quiet grace. She never questioned his increased presence, never pointed out that his excuses for seeking her company were often flimsy at best. Instead, she simply made room for him in her world of books and spells and magical research, sharing her discoveries with him in that soft, thoughtful voice of hers.

They had their conversation, eventually—a long, honest discussion about feelings and intentions and what they meant to each other. It had been awkward at times, given [Y/n]'s reserved nature and Rimuru's tendency to overthink, but they'd worked through it together.

And yes, they still kissed— Frequently, in fact. But now it was a conscious choice rather than a heat-driven necessity. Now it was an expression of affection, of connection, of the deep bond that had formed between two slimes who had found something precious in each other.

As for Shuna, she had indeed been discreet, though Rimuru suspected she'd shared what she'd seen with at least Benimaru and Shion based on the knowing looks he'd been receiving. But the gossip never spread beyond his closest circle, and for that he was grateful.

One evening, several weeks after the heatwave had passed, Rimuru found [Y/n] in her usual spot in the library. She was absorbed in a new tome she'd acquired—something about advanced ice magic, naturally—and didn't notice his approach until he was right beside her.

"Find anything interesting?" He asked, peering over her shoulder.

"A variation on Diamond Dust," [Y/n] replied without looking up, her finger tracing the lines of arcane script. "It combines ice crystals with light refraction to create a defensive barrier that's both beautiful and functional. I've been trying to work out the mathematical formula for optimal crystal formation."

"Of course you have," Rimuru said fondly. He pressed a kiss to the top of her head, and she finally looked up at him, a small smile playing at her lips.

"Did you need something?" She asked.

"No," He admitted. "I just wanted to see you."

That smile widened slightly, transforming her usually serious expression into something softer, warmer. "Then stay," She invited, scooting over slightly to make room for him beside her. "I can explain the spell structure if you're interested."

Rimuru settled in next to her, close enough that their shoulders touched. "I'm always interested in what you have to say."

And as [Y/n] began to explain the intricate details of ice crystal formation and light refraction, her quiet voice filling the peaceful silence of the library, Rimuru reflected on how grateful he was for that ridiculous heatwave. Without it, he might never have discovered just how essential [Y/n] had become to his life—not as a cooling system, but as a partner, a confidant, and someone he was beginning to realize he couldn't imagine living without.

The heat had been a catalyst, but what it had sparked was something far more valuable than simple temperature regulation.

It had sparked love.