"... Looks like it's going to snow."

Mercenary lowered his hands from where he had been cupping them around his eyes, as though using a pair of binoculars.

"Hey, Little Witch, is it really alright to go out in this weather?"

"Don't worry. In the worst-case scenario, I can just use magic to keep us warm."

"That's unnecessary. You should save it for later. After all, we're going to be facing plenty of hardships from now on."

Mercenary frowned. He disapproved of Zero using magic so carelessly, and for good reason- she could only turn him back into a human after she gathered enough magical power. Contrary to his expectations, though, Zero looked delighted.

"That's alright. Then, we'll just have to warm up the old-fashioned way."

"The old-fashioned way?"

Mercenary did not like the sudden glint in Zero's eyes.

"Yes. The best way to warm up is to share body heat, after all."

"Oh. If it's just that... You already do that, under the pretense of enjoying my fur."

"But I really do enjoy your fur. I envy how fluffy it is."

"Whatever."

He sighed and turned away from the petite, white-haired witch. Though she was the genius that had written the Book of Zero, a priceless treasure which was essentially a guidebook to using magic, she acted awfully childish at times.

"Let's go find a place to have dinner."

"Hey, innkeeper! How bad do you think the snow's going to be?"

The innkeeper, a burly, tanned man with a red bandanna around his head, shrugged.

"Don't know. This time of the year, the amount of snow varies year by year. Just last year the pass was completely blocked off, but the year before that it was completely fine."

"I see."

Mercenary sighed. Going through the pass now rather than later was a risky gamble. With Zero's magic they might not freeze to death, but it was still dangerous to navigate a snowed-in mountain pass. However, the delay could allow their target to escape before they could confirm and confiscate the illegal copy of the Book of Zero the target held.

'Seriously, why does everything turn out so ridiculously complicated? It's all that stupid witch's fault. If she just hadn't written that stupid book, then-'

He didn't go any further with that train of thought. Though he seemed extremely grumpy on the outside, he was still sincerely grateful to have met Zero on the fateful day when he had fallen off a cliff onto a pot of soup.

"Hey, hey, Mercenary. Let's get going."

"Are you insane? It's evening. I wouldn't want to get caught out in the snow at night. We'll stay here for the night and continue onwards tomorrow."

Zero pouted, and Mercenary fought the urge to sigh in exasperation.

'It's all for her sake, anyway! I don't want her to freeze to death or get lost wandering around in a blizzard!'

"Are you done yet?"

"Aumosht." (Almost.)

Zero's mouth was stuffed full with food, and she swallowed it all with a single, huge gulp.

"Ah, I'm full. Is there any sensation better than having a full stomach?"

"I can't argue with that myself. Sleeping next to a warm fire also feels pretty good, though."

"True. But in my opinion, food still reigns supreme."

"Yeah, yeah, whatever you say. We should retire for the night."

Mercenary and Zero made their way to their respective rooms. Mercenary mumbled a short "Good night" and fell on his bed. It was rare to find an inn that treated beastfallen like him so well.

Within minutes, he had surrendered himself to the soft embrace of the mattress, and the sound of soft snoring filled the room. And then, the door creaked open.

Mercenary opened his eyes to feel a familiar weight on his chest, and sighed.

"I don't even know why I try anymore. With you, paying for two rooms is a waste."

"Blame your own fur for being so soft and fluffy. It's gotten to the point where I can't sleep without it."

Zero said, woken by Mercenary's grumbling. With an annoyed expression on her face, she clutched him tightly while rubbing her face against his chest.

"You're really impossible, aren't you."

He stood up, Zero still hanging on to him, and got dressed after gently disengaging Zero.

"You should go get dressed, too. We have a long day in front of us."

After having breakfast in the inn- black bread and goat cheese- the duo left the town, headed for the mountain. The journey was grueling, as the already steep mountain was slick and slippery from the snow. In some parts Mercenary had to discard his boots and hold Zero while moving forward, confident in the abilities of his paws and claws to find purchase on the ground.

As they forged onwards, the snow gradually became thicker and thicker, and then suddenly they were assailed by a blizzard. The strong winds caused Zero to trip and almost fall, but she was caught by Mercenary before she reached the ground. Both of their clothes were soaked from sleet, and they were both in danger of hypothermia. Mercenary's fur wasn't much good in this situation, as it had become waterlogged and thus susceptible to cold.

'Dammit. We've got to find a place to rest.'

Mercenary desperately looked around, and saw a cave leading into the mountain. Though such caves had a high probability of housing dangerous animals like bears, he would rather take on a bear than freeze to death. Carrying the shivering Zero in his arms, he went inside the cave as quickly as he could, and collapsed, panting. It was a truly dismal situation- he had no firewood to start a fire with, and even if he did it would be too wet to use without filling the cave with smoke. Zero was in bad condition, which meant her magic, the only thing he thought could save them in this situation, was unavailable.

First, he stripped himself of his wet clothing. Keeping it on would only hasten his death. He hesitated before taking off Zero's clothes, but resolved himself with the thought that he would rather have to see her naked than see her die. While looking away, Mercenary peeled the clothes off her, face bright red despite the white fur covering it.

His fur was a problem. He couldn't simply take it off like he had done with the clothes, but it would kill him sooner or later. Sobbing loudly inside his mind, Mercenary reached for the knife inside his travel bags.

And then he felt a soft touch on his arm, and realized Zero had extended a trembling hand to him. With a weak snap of her fingers, she applied on him the same drying magic he had first seen so long ago, back when she had helped him bathe. And then, exhausted, she collapsed, and Mercenary touched her forehead before drawing back in shock due to how cold she was. He immediately gathered her into his embrace, covering her with his thick fur. Though they didn't have a fire, they weren't wet, and they were out of the snow. They had a chance of getting through this alive.

Though, the excessive skinship was making Mercenary extremely uncomfortable. He tried his best to rationalize it by telling himself sharing body heat was the only way to survive, but it still didn't stop the red flush from appearing on his face. Mercenary, a man who was paid to kill, and who had killed numerous times, was embarrased about being so near a naked woman.

He grasped around in the travel bags and fished out some hard deer jerky, gnawing on it while he leaned against one side of the cave, listening to the sound of the howling winds outside. When would the blizzard abate? Could they even make it through to the other side? Such thoughts flew around Mercenary's mind as he closed his eyes and fell into a deep slumber from sheer exhaustion despite how early in the day it was.

Mercenary woke up and stretched, yawning. He was still very cold, but he wasn't dead, and that was a definite plus.

"Good morning- or should I say good night?"

"What?"

On top of him was Zero, who was straddling his belly. This normally wouldn't be a problem, if not for the fact that she was naked. And so was he. Panicking, he tried to move out from under her, but found that he couldn't move a single inch.

"What are you doing, Zero?!"

Mercenary roared. He didn't believe Zero would betray him, but still...

"Isn't it obvious? I got tired of waiting for you to make a move on me, so I decided to take the initiative."

"Huh?"

The unexpected answer shocked him, and his face grew scarlet. Zero poked his chest with a slender finger, and drew it downwards, tracing shapes into his fur. Mercenary's face, which was already cherry-red, seemed to emit steam from how embarassed he was.

Zero got off him, and moved over to his legs.

"I see that my memory does not fail me. So this, then, is a penis."

"Where the hell did you learn that word?"

Mercenary yelled.

"The anatomy of a human being was part of the education we received in the caves. Although this is only my second time seeing one in person..."

The first time had been when Mercenary, after bathing, had forgotten he was naked and had stood up, exposing his body to Zero (and Albus, who just happened to be standing there).

"Though it does look different from the diagrams. Perhaps it is because you are a beastfallen, and not a human? The base structure seems to be the same, at least."

Zero poked it with her finger, her expression inscrutable.

Mercenary once again tried to struggle, but Zero's magic kept him tightly bound.

"Stop! What would Albus say if she saw this? What would Thirteenth say?"

"Albus would probably say that it's impure, and that you're the embodiment of depravity. As for Thirteenth, you know just as well as I do that I don't care a single whit for the garbage he spews from his mouth."

Mercenary took out the last card he could play.

"We're in the middle of a blizzard! Shouldn't you be, I don't know, more cautious?"

"What, am I doing something wrong?"

"Yes! In many ways!"

"How so? I'm sharing body heat with you, aren't I?"

"S, still-"

"I see no problem with the current situation."

Zero said, her eyes still fixated on Mercenary's penis, which had begun to grow erect from her touches.

'Shit! Calm down, calm down. I said calm down!'

"I see. So this part becomes engorged with blood. Very interesting. Now-"

A slight flush had come onto Zero's own cheeks as well.

"- Let's taste it."

"Hah?"

Zero lay down between his legs, and grasped Mercenary's penis with both hands, bringing it to hrr mouth. She stuck her tongue out and licked it once, before frowning.

"Hmm. Doesn't really taste good, but I suppose that's not the point."

"Don't treat my- my groin as though it's food! Also, where did you learn this? Don't tell me it's another thing you learned in the caves?"

"No, it's something I read in a book at one of the bookstores we stopped by. It was very... Informative."

"That's not any better!"

Any further complaints he had were cut off when Zero suddenly took the tip of his penis into her mouth, entirely engulfing his glans. She stayed that way for a few moments, becoming accustomed to the foreign object inside her mouth, and slowly began working her head back and forth.

Mercenary was torn. On one hand, it felt good, and he certainly had feelings for Zero. On the other, it was Zero doing it, and that fact somehow made the situation feel... Wrong.

Zero was now attempting to reach the base of his penis with her mouth without triggering her gag reflex, but ultimately failed and rose for breath while coughing.

"Are you okay?"

She waved away his concerns, and went back to working on his penis. She was certaiy very skillful for the beginner she was- just how detailed had the dirty book she read been?

Part of Mercenary's mind was in bliss. Every time her teeth lightly scraped along his shaft, every time her tongue brushed against the tip, every time she blew on it slightly, he felt as though he was ascending to heaven. The other part of his mind rejected what was happening. Zero is a witch, that part said. You hate witches. You're only working with her because she said she will turn you back into a human.

But she's Zero. Said the euphoric part of his mind. Zero is someone special to me. She is the only person I would follow out of my own volition.

And then he felt an inevitable tugging in his balls, and he cried out in pleasure as he ejaculated, spraying the inside of Zero's mouth with whitish fluid.

"I'm so sorry! I didn't mean to-"

Mercenary attempted to apologize, but was completely ignored by Zero, who ran a finger over her lips, staring at the liquid. Then, she swallowed.

"So, this is semen... What a unique taste. I... Could get used to this."

Mercenary's and Zero's eyes met, as she slowly crawled closer to his face, making sure her body was in contact with his at all times. Soon, she was lying on top of him in much the same way as how she typically slept, but without clothes.

Zero reached out and caressed the side of Mercenary's face with her hand, and brought her face up to kiss him. It was a surprisingly chaste kiss- a peck on the lips, but one that lasted for several seconds.

As Zero positioned herself over Mercenary's penis, he began panicking once more. After all, he was a virgin. Furthermore, Zero was just as beautiful as she often claimed to be. Zero picked up on his agitation and chuckled.

"What's the matter, Mercenary? Could it be that you're a virgin?"

She clapped her hands over her mouth in mock horror while grinning widely, prompting Mercenary to look away in embarassment.

And then her expression quickly turned serious, with no trace of her former smile.

"If you don't want me to do it, I will not force you to."

She said.

A long pause.

Then-

"If it's you... I don't really mind."

Muttered Mercenary, trying his best to look everywhere but at Zero's face, which displayed a soft smile.

She lowered her slim hips, touching the head of his penis to the outer lips of her labia. There, she moved in small increments, rubbing it against the slit between them.

And then she began to put more force into her hips, slowly driving them downwards. Mercenary's penis began spreading her labia, and then it was at the opening to Zero's vagina, and then, with a bit of extra effort from her, the tip popped inside.

"Ah, aah!"

She raised her voice involuntarily from the sudden insertion. The experience was nothing like sex with a human- humans did not have the barbed shafts that felines did, and as a tiger beastfallen it was a trait Mercenary shared with them. And then, she continued pressing herself down on Mercenary, the penis delving ever deeper, until it met a barrier. A thin, fleshy barrier. One that Zero broke through with no hesitation at all. After all, she had received permission from Mercenary, and she herself had no qualms with giving her virginity to him.

When her hymen tore, a sharp sting was felt, and a small amount of blood oozed its way out of her vagina.

"Does it hurt?"

Mercenary asked, concerned. Zero, after a moment's deliberation, shook her head, her long hair swaying along with the motion.

It only took a little more for the penis to reach the entrance to her womb; after all, Mercenary was a big man, and his member matched his size, while Zero was small, around as small as Albus, who was but a child. There was still some length left to Mercenary's penis, but attempting to force it in would be pointless- Zero simply had no more room to give.

And then came the part where the dick was pulled out of her. Her mouth opened in wordless pleasure as she lifted her hips, and the penis retraced its route in. And, with a wet noise, the head popped free, and Zero put it to her lower lips again to repeat the cycle.

This time, her speed was faster, her breathing rougher and more frequent. Faster and faster she moved, until she was bouncing on top of his penis, moaning in pleasure. Her moans and his grunts harmonized as they both drew closer and closer to the climax.

And then, with a bestial roar from Mercenary and a high-pitched moan from Zero, they climaxed at the same time, Zero's vagine clamping down on Mercenary's penis as it swelled slightly, delivering his hot seed into her vagina, where it overflowed and came splashing back out.

The two lay there, panting while basking in the post-coital pleasure. Two gazes met- one, shy but caring, the other filled with fierce love.

Suddenly, Zero smiled mischievously.

"Up for another round?"

In the end, they ended up going at it until they both collapsed from exhaustion. The next morning, the two used melted snow to wash themselves clean. Zero insisted on scrubbing Mercenary's back, "like old times".

As she scrubbed away, she brought her lips to his ear, and whispered softly.

"Take responsibility."

Mercenary jumped in surprise, while Zero fell backwards, cackling. He turned and glared at her, but she paid no heed and continued laughing. His glare turned into a sigh and a wry smile.

'In the end, she's still Zero, through and through.'

"Hey, Mercenary."

"Hm?"

"I think I've found a sensation that I like more than having a full stomach."

The blizzard had stopped, and only a very light snow was falling from the sky. The two continued their journey, and made it to the other side in the same day.

Though they made it a point not to discuss it in front of others, people who knew the two commented that they seemed to have grown closer. Somehow, Thirteenth found out about what happened, and personally journeyed out to beat Mercenary up using magic, after which Zero beat Thirteenth up in return. But that's another story, for a later date. For now, the curtains close on the love the two shared while stranded inside a mountainside cave.

Notes:

Thank you for reading this short story! As my first attempt at smut, I was worried it would be too difficult to write, but it went over surprisingly smoothly.

I have only read the first volume of Zero (the first season of the anime), and so my knowledge regarding the lore and backstory is rather lacking. I purposefully did not include any magic that would require incantations and such, as I was tok lazy to go back and look them up.

As this is a fanfiction, please treat it as the daydreams of someone obsessed with shipping Zero and Mercenary.