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There are few things that Frieren hates more than the winter. Truth be told, one would be hard pressed to find a kind of weather that she likes that isn't perfectly mild. The thousand years she has spent alive have not increased her hardiness one bit. They have taught her, instead, that there is a very narrow range of temperatures in which she operates with optimal efficiency. Outside of that range, whether it be too hot or too cold, she is beset by everything from lethargy to a complete lack of will to do anything at all.
She wonders, sometimes, if elves are the closest thing that a mammal might get to being truly cold-blooded. Her body, it seems, relies almost entirely on her environment for temperature regulation. It is the most logical separation; an anatomical oddity of her species that makes her fare much worse in extreme temperatures than her warm-blooded companions.
Himmel especially.
She notices this for the first time when they are en route between villages, and Himmel insists on using the slushy white refuse left behind by the last snowstorm to engage in the barbaric practice that humans call snowball fights. Frieren, still a little traumatized from when Flamme inflicted these very horrors upon her as a child, declined to participate. So she stands very still to conserve as much body heat as she can, limbs quivering as she watches Eisen, Heiter, and Himmel pelt each other with small, wet projectiles.
"Are you sure you don't want to join us?" Himmel calls out to her from across a snow-covered glade, so thick that he is buried in it up to his ankles.
Frieren shakes her head in the negative, and the cold wind bites her skin even as she does so. She watches forlornly as the three idiots who somehow convinced her to be their companion waste the precious time they ought to be spending on getting to the nearest inn with a fireplace and good insulation.
Then, Himmel pauses mid-throw, turning to look at her with a frown. For a moment, Frieren is afraid that she will be coerced into joining this snowball fight despite her desperate wishes to the contrary, but nothing of that sort happens. Instead, he walks towards her, unclips his cloak from around his neck, and sets it on her shoulders. The lingering warmth from his body diffuses through her skin, and Frieren lets out a happy sigh of relief when he firmly pulls the hood of the cloak over her reddened ears.
"Better?" Himmel asks her, ducking his head so that she does not have to lift hers.
"Mhm," she answers, too cold to open her frostbitten lips.
He straightens, puts a hand on the back of her head, and leans forward as though to whisper something in her ear. But he aborts the motion halfway through, retreating back towards the chaos of the snowball fight. A strange thought strikes her, then. It isn't strange in that it is novel; rather, the intensity with which she comes to this realization is quite unprecedented. Himmel is warm. He always has been, as far back as she can remember. The cloak around her body is still warm from when it was his.
The thought stays with her even as they finally, finally retire to an inn. Her room does not, much to her dismay, come outfitted with a fireplace, but the shuttered windows and fluffy comforter promise some well-needed reprieve from the bitter cold. Himmel turns in at around ten—he's usually the first one to sleep and the first one to rise—and Frieren settles into her own bed with a grimoire in her lap. She watches the rise and fall of his chest for a moment before pulling her own blanket over her head. By the time she is halfway through the grimoire, her eyes are losing the fight to stay open.
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It is cold.
No matter how much her muscles quiver, she feels it seep under her skin and into her nerves. The sound made by her chattering teeth chases her into her dreams. She curls into a ball to conserve what heat she can within the confines of her body. It works for a time, but a stray draft pierces the careful bubble of warmth she has built around herself like an arrow, and it hurts.
And then, it stops.
She is surrounded on all sides by the softest, sweetest warmth she has ever felt in her entire life. It seeps through her skin and into her bones, quieting the motion of her shivering muscles. She feels like she's being enveloped by a cloud. She wants to stay here forever. But when she tries to get closer to it, it pulls away from her. Soon, it has left her entirely, and her skin aches with the ghost of the warmth that should have been hers to keep by right.
"There you go," the warmth says, gathering her close for a brief moment, before the sensation of being jostled fully awakens her.
Frieren is able to catch only a brief glance at Himmel before her bleary eyes protest being open for more than even a fraction of a second. She watches as he tucks her back into her bed and carefully brings the comforter up to her chin. His hand is warm when he presses it against her forehead for a brief moment before retreating back to his own bed, taking all the warmth with him. It feels like a loss, somehow. For the life of her, she cannot begin to fathom why that would be.
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Ever since they started on their journey, Frieren and Himmel have always shared a room. She remembers that Himmel had initially been awfully resistant to the idea. He turned a very funny shade of pink, sputtering with so much intensity that he could barely get a sentence out, before he insisted, "That's indecent and ungentlemanly."
"Your sleeping arrangements will only ever be as indecent as you are," Heiter retorted before accepting a pair of key rings from the innkeeper. And ever since then, that has been the status quo.
Frieren is also, contrary to popular belief, in possession of something akin to self-awareness. She has been a restless sleeper as far back as she can recall, tossing and turning more than is physiologically necessary to relieve pressure or improve blood circulation. She often wakes up with her body folded in strange angles, giving her back and neck especially no end of trouble. Because these nightly position changes tend to have a…a rather large radius of movement, she often winds up in Himmel's bed.
She is aware of this only because he always makes it a point to return her to her own bed. Sometimes he lingers, and there is enough light in the room that she can see him smile. It is a strange smile, visible only in the barest twitch of his lips, and she has never seen it before in any other context.
But why?
Frieren has a hypothesis that she wants to test, because she wholeheartedly believes that there is a perfectly logical explanation for this behavior. The second law of thermodynamics states that heat flows hot to cold. Frieren's subconscious must have known this, hence her seeking Himmel out by night to facilitate a proper transfer of heat. This inspires Frieren's first experiment, which she begins on a bitterly cold January night, seeking to compare this behavior to the overwintering habits of other creatures.
Himmel, who is buttoning up his nightshirt with his back to her, turns around to catch a glimpse of her scribbling furiously in her notebook. "What're you writing?"
"I am conducting a controlled experiment about the overwintering habits of elves," Frieren replies, eyes not lifting from the page for one moment. She casts a quick spell to measure the room's temperature from the average velocity of the particles in the air, makes another note, and sets the notebook aside.
To not confound the experiment by deviating from her usual sleeping habits, Frieren turns her attention to a grimoire with a spell for cleaning out the dirt from underneath one's nails. It holds her interest for at least a few hours past when Himmel has gone to sleep, and when she can feel the slow onset of drowsiness as her body begins to shut down, she sets this book aside too. She falls asleep expecting for another dreamless night, but she is instead accosted by the most unsightly of nightmares.
Frieren doesn't know whether she should be glad that she is perfectly lucid, because all of her conscious efforts to redirect her thoughts feel like she is trying to scale a sheer rock face in the rain. She keeps slipping, and she has no other words to describe her growing frustration with herself as her mind keeps replaying an old memory of a confrontation with an enemy she would very much rather forget. She feels her right arm grow heavy and numb, even when she understands that it should be perfectly fine, and—
"Shh."
Huh?
"It's okay. I've got you."
Is that Himmel?
Frieren looks up at him, wanting to explain the second law of thermodynamics. Himmel frowns down at her in a way that makes her doubt she understood a word of what she said. She isn't very surprised that she is in his bed; the window is covered in frost from the outside, and the inside of the room is not much better. What does surprise her is that he's not engaged in his usual routine of returning her to her own bed.
"'M not going anywhere, okay?" he yawns. "So rest easy."
But when she wakes up in the next day, well into the afternoon, she is still in his bed, though Himmel is long gone. With a frown on her face she cannot fully explain, she makes a tally mark on her notepad.
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As she makes more observations, Frieren notices a pattern that broadly supports her hypothesis. Namely that the colder it is, the more likely it will be that she winds up in Himmel's bed. Her own behavior is perfectly rational, and can be explained by basic facts of thermodynamics, but Himmel's puzzles her. Why is his usual pattern to return her to the cold nest of blankets she so desperately fights to leave behind? What, if anything, makes him deviate from this pattern?
But it is firmly the middle of spring, well on the way to summer, when Frieren even begins to consider this line of inquiry. The nights have gotten warm, too warm for her to use the comforter she so adores come winter, and though Frieren often finds herself ousted from her bed in odd position, she is rarely sprawled across Himmel's instead. She decides, then, to use what she knows about the temperature and how it correlates to her own habit to control for these…confounding circumstances.
Himmel is brushing his teeth in the adjoining bathroom when he emerges, foam still on his chin, to announce his observation to Frieren. "It's getting chilly tonight, don't you think?"
Frieren's stomach ties itself into a knot when she sees how he hugs himself, short-sleeved cotton shirt too thin to withstand the spell she is casting. "I am rather inclined to agree."
"That's a lot of words for agreement."
"They were all necessary."
He shakes his head, and there's that smile again. "Whatever you say, Frieren."
Like clockwork, Frieren worms her way into Himmel's bed after she falls asleep. Like clockwork, she is promptly returned and tucked in with exacting care. What troubles her, both in its novelty and its stubborn refusal to be easily categorized, is the disappointment she feels when she records this in her notepad.
It must be the cold, she thinks.
What else could it possibly be?
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One of the first lessons Flamme drilled into Frieren was the importance of academic rigor. This is why she casts the spell to lower the room's temperature despite her lack of interest in continuing the experiment. She needs multiple observations to come to an airtight conclusion, after all. Still, she takes the time to gather her thoughts thus far, if only to remember them later. Given the variables I have considered so far, she writes, I have reason to believe that Himmel's habits in this regard are not responses to his needs, but what he perceives to be my own.
That makes sense, doesn't it? I've got you, he said, and then he carried on like he meant it. He must have thought he was giving her comfort in response to her distress. So if Frieren really wants to understand him, she has to ignore the outliers, because they were really only caused by changes in her behavior. And over and over, Himmel has proved to her that the only thing he wants is…is to be rid of her.
How had she not noticed before?
From the lens of thermodynamics, this makes perfect sense. After all, she is a leech, stealing the warmth from his skin and bones and hoarding it into her own person. Frieren does not blame herself for the way that the universe has decided the laws of physics should work. But she also repeatedly caused circumstances that Himmel is clearly averse to for the sake of an experiment whose results she could have reached with simple deduction.
Frieren brings her grimoire up to cover her face, and watches Himmel intently when flipping between pages. As if detecting her scrutiny despite the expert technique with which she is hiding her insightful gaze, Himmel turns away from her after snuffing out the candle.
"I thought tonight would be warmer," is all he says, yawning into his palm.
She tries to reinfuse the energy she has drained from the air to forcibly lower its temperature, but her concentration fails her even as she endeavors to cast this simplest of spells. She feels a very heavy lump in her throat that must be a piece of food stuck there from dinner, but it refuses to be dislodged no matter how forcibly she swallows. Cold and with no real means to warm herself, Frieren slips out of her bed and pads towards Himmel's.
"It's late, you know. Even for you."
She stills at the unmistakable sound of Himmel's voice. "Is it?"
Himmel pillows his head on one arm so that he can lift his head to look up at her. "What are you doin' up?"
Frieren stands there for a moment, silently weighing her two options. She could return to her own bed and pretend that this never happened and hope, for the sake of her own dignity, that Himmel will have the courtesy to pretend as well. Or, she could confess the results of her study and present Himmel with a perfectly rational explanation as to why they must sleep in the same bed tonight. Option one is, on every level, the better choice. But. But. Her bed is so far away, and it is so very late at night, and Himmel is so warm, and so, so close.
"You see," she starts, "the second law of thermodynamics describes the process by which heat—"
"Frieren."
He does not say her name very loudly, but it makes her thoughts spiral into the void as she scrambles to course correct. Conversations are decision trees to her, built upon years and years of learning conditional probability to predict the next appropriate thing to say. But she has no frame of reference for the way he is looking up at her, light shining in his blue eyes even in a room that is otherwise near pitch black. Then he smiles, the barest twitch of his lips, something that doesn't fit into the otherwise easy categories that make Himmel up.
"You don't have to justify asking me for anything," he says very gently. "You know that, don't you?"
Frieren files this information away for later, still stunned into silence, because in no way could she have predicted that would be his response. Then he lifts up the edge of his blanket and gingerly pats the empty spot beside him in his already narrow twin bed. Frieren slips under the cover with ease that is much more practiced than she would like to admit. When he lays the blanket back down on the two of them, his hand loosely settles around her back. She lets out an involuntary sigh at the sudden rush of warmth.
"'S this alright?"
"Mhm," she replies.
Himmel then pulls her flush against him, tucking her head under his chin. Frieren presses as close to the warmth of his chest as she can, so that the principles of thermodynamics will be on her side. After all, larger surface areas allow for more efficient transfers of heat between touching bodies. She is just utilizing the laws of physics for her own advantage. She balls her fists in the soft cotton of his shirt, too tired to thank him in words.
"You really like this, huh?" Himmel laughs, running a hand through her hair to settle it at the back of her neck.
"Mhm."
He kisses her forehead, which makes a sudden rush of heat bloom at the point of contact between them. Frieren catalogues this phenomenon as an objective observer, finding that no equation she can think of can explain why her cheeks feel so very flushed and heavy. She is gripped by the irrational fear that even in the dark, with his eyes closed, Himmel can tell. That would be preposterous. Nobody can see in the dark, not even someone as canny as Himmel.
"G'night," he tells her with a yawn, and when she carefully snakes her hands around his torso, she can feel him relaxing into her arms.
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Himmel has trained himself to not read too much into Frieren's behaviors, because he knows then that he will start to see things that he knows are most definitely not there. Like a desire to be close to him, or fondness for him beyond the amiability she extends to everybody else in the party. Still, come morning, the first thing Heiter says between loud yawns is, "Goddess, our room was like a sweatshop tonight."
And his brain sort of short circuits.
Because as far as he knows, his room is identical to the one Heiter shares with Eisen. Both have one window opening out to the city, and neither is outfitted with light fixtures or candles that the other doesn't have. So the only logical explanation is that someone must have artificially lowered the temperature in his room. Who would have done so?
How?
Why?
"Frieren," he asks cautiously when their party has retired after a day spent weeding a cabbage patch and grazing a herd of unruly sheep.. "Do you want to sleep in my bed?"
"Not particularly."
And there it is. The complete lack of inflection he usually is quite fond of but now causes him great pain.
"Then why…?"
"I thought I told you. I was conducting a study on the second law of thermodynamics."
"Wasn't it the wintering habits of elves?"
"Overwintering," she corrects. "The second law of thermodynamics is the explanation."
Himmel barely understands a word of what she said, but the sentiment is clear. These are all numbers to her, empirical observations that will never mean as much as he wants them to. Still, he wishes that—
No.
Wishing never helped anybody, least of all him.
All it will do is teach him to get his hopes up when there really is no reason to.