The butterfly estate, as well as the whole Demon Slayer Corps, was not in a good mood. With all the gloomy stuff that seemed to torment its members lately, they could barely be able to concentrate on slaying demons as per usual. Oyakata-sama was kind enough to understand Shinobu's decision of staying inside the estate, without going into missions, in the hopes of finding something that would prove helpful to your health. It had only been two days, but she was slowly losing hope of ever getting a cure, and everyone else knew that too.

The mist pillar, though, was by far the person whose heart had been devoided of any color whatsoever. He knew that if anything happened to you, he would never be able to feel anything again, like an empty shell, without an ounce of care, worse than how he was before.

His mint-colored eyes were fixed on the apple he was peeling for you to eat, their emptiness now greater as the tiredness of his face due to his anxiety and worry of losing you became greater. Meanwhile, you were looking outside the window to nothing in particular, mainly ashamed of your own decrepit state.

"STOP BEING A CRYBABY AND STAY STILL!"

"THAT'S GONNA KILL ME! YOU'RE TRYING TO KILL ME!"

"ZENITSU— WHERE ARE YOU RUNNING—?"

The silence you two were peacefully engulfed in was interrupted by loud yelling coming from the room next to yours. Muichiro muttered some curses, angered that the loud sounds would disturb you in any way, but when he turned to look at you, his eyes met your shimmering ones. His shoulders slumped as a small, almost invisible smile made it's way to his defeated features. At the very least, you seemed curious to know the source of the yelling, which in turn made you happy, and he adored seeing you like that.

Aoi walked in fuming with anger, but she managed to calm herself down in order to talk to you. "Sorry for the noise, there's some... problems with other patients"

You could barely hold your laughter, puffing your cheeks and covering your mouth with your hands, as you saw her dragging two boys, one on each hand, both badly beaten up by her.

"I-It's fine! Uhm... can I know what all that noise was about?" your eyes instantly deviate towards the two boys again, "Were they on a mission?"

"Ah, well..."

Before Aoi could even finish up a single sentence, one of the boys —the blond one with noddle arms— escaped from her grasp as soon as he heard your female voice. He rushed at the feet of your bed with eyes that cried fountains and tugged your white clothing as if he was begging for something.

"PLEASE, PLEASE, PLEASE MARRY ME! I DON'T HAVE MORE TIME, I MIGHT DIE ANY MINUTE! MARRY ME!"

You blinked multiple times, processing the words that boy had just yelled at you. After a couple seconds of your brain trying to work properly, you let out a loud laugh.

"What a coincidence, I'm about to die too! Should I get married?"

"Then... then..." Zenitsu's eyes shone as the tears kept sliding down his reddish cheeks "Are you going to marry me?"

You closed your eyes and gave him the kindest smile possible, "No. My heart solely belongs to my master."

"BUT—"

A cold blade lightly scratched Zenitsu's cheek and hit the wall behind him, getting stuck into it and probably leaving a hole. The boy's whole body shook, getting chills, as his heart slipped a beat. He felt a hot liquid sliding down his left cheek just how his tears were seconds ago.

It missed his head for a couple centimeters, but it left a small diagonal cut on his cheek in exchange.

Trembling, he looked towards Muichiro's cold stare, a murderous and dark aura surrounding him.

"Sorry, it slipped right through my fingers." he said, looking down on the poor boy with a bone-chilling stare.

Zenitsu screeched for his dear life and immediately rushed to hide behind you the best way he could. Meanwhile, you felt your cheeks heat up, taking them both between your hands and looking away with a certain shyness.

"Tokito-sama is so cute when he's jealous... I have such a cute future husband!"

"Y-YOU CALL THAT CUTE?!"

You giggled at his reaction, but promptly turned back to the first question you had when Aoi came in. "So, what exactly happened? The whole estate is awfully silent, and outside of my health, I've seen some other demon slayers passing by muttering prayers and crying"

"Ah..." Aoi looked away as the atmosphere became tense. She coughed twice, almost hesitant of answering, but decided to indulge your curiosity instead of leaving you in the dark. "The night you came in here, Rengoku-san... the flame pillar, died at the hands of upper moon three. These two were also on that mission with him."

A gasp escaped your lips as your eyes widened, caught off by the words of the blue-eyed nurse.

"Did you know?" the question fell out of your lips lifelessly as you turned towards Muichiro, whose answer was as dry as a simple nod.

Aoi let out a sigh, walking deeper into the room to get the blond boy to his own room. "The news came when you were still sleeping. Shinobu said not to disturb you with troubling news since they could worsen your condition, but..." she stopped abruptly when she noticed the pained look in your face. Between the fact that she had just disobeyed her superior's orders and her duty of giving the boys their medicine, she rathered to shut up and get out of there.

Your hands wrinkled the fabric of the sheets, your heart feeling the anguish of what being a demon slayer really meant.

"Even the strongest demon slayers can die too, huh? Does that mean that even if I get better, Shinobu, Giyuu and you will die and leave me alone?"

"That isn't going to happen."

"How do you know? I was idealistic enough to think that death would never come to us, but I'm dying now and any of you might be next"

Silence stayed for about two minutes. A silence that held nothing but the sad reality you lived in.

Until you felt two delicate hands gently take your cheeks, fixating your eyes in the bluish ones that kept making your heart beat faster.

"I'm not going to leave you alone. Shinobu is doing everything she can to find something that can help you, so don't cry. Everything's going to be fine, I promise."

It was one of the only times you got to see Muichiro smile sweetly; the kind of smile you give to the person whom your heart belongs to.

『 °*• ❈ •*°』

It had been a week since then. Everyone at the estate worked tirelessly to help Shinobu in any way they could, while taking care of you. Your condition wasn't getting any better. You had gotten so thin to the point of your bones showing unhealthily beneath your flesh, the tips of your fingers had taken a bluish color, your chest hurt like hell and fatigue took a huge toll on you even though you barely got out of the bed.

Later that day, the golds and oranges of the blazing sun sneaked through the window of the insect pillar's research room, caressing her softly, as she seemed to have fallen asleep on her desk over the piles of paperwork scattered there. Shinobu was the type of woman that was gifted the beauty and grace of the heavens, with long eyelashes that would flutter like a butterfly's multicolored wings and petite soft lips, and her ability to conceal her true feelings was even more worthy of applause.

But even if she tried, there were a few people who had noticed her restlessness. Among them, was none other than the water pillar himself.

When she opened her eyes after being greeted by the not-so-subtle sunlight shining through the room, the first thing she noticed apart from the small string of dry saliva over her paperwork (which had made her embarrassed inmediatly), was long black hair and a mismatched haori.

He was sitting on the floor, back leaning against the door. He wasn't facing her, and rather seemed to be checking his sword or something along those lines.

She mentally frowned, but managed to easily show a mocking smile to address him.

"Ara, ara~! Watching girls while they sleep? Tomioka-san, you get creepier each day. Is it a specialty of yours?"

Giyuu simply glanced at her for a second, unexpressive as always, and returned to pay attention to his sword.

An irk mark thickened on the woman's forehead by the man's reaction. "That rudeness of his is why he has no friends, goodness."

She sighed to herself, wondering why he would be present on her research room out of all places.

In truth, Giyuu would always go visit you after his missions. He couldn't fully understand why he began caring so much about you, but maybe it was the fact that such a dear person to him was suffering, that lead him to show a little more emotion and concern. In that aspect, he found you similar to Tanjiro.

This day he had passed by the wide open research room and noticed Shinobu sleeping there. He knew that she had not slept for three days straight and kept herself awake with coffee and tea. The dark circles under her eyes and the way she was sleeping —over her desk, meaning that she likely fell asleep unintentionally—, told him so.

Thus, he decided to make sure nobody else bothered her so she could get enough sleep, specially because the estate had been very loud lately due to three loud demon slayers training to get their condition back up.

But of course, Shinobu had more important matters to attend to rather than questioning the water pillar's actions.

"Seriously, you're so useless. You should've just woken me up."

Giyuu's cold ocean eyes spared her another look, "Okay. Did you sleep well?"

"That doesn't matter!"

He titled his head a little, lightly showing how confused he was by her words. Shinobu then proudly stood up from her chair, smiling radiantly with a determined look.

"You might as well be useful for once. Go gather the pillars and kakushi that aren't busy with important stuff, fast."

"...Why?"

Shinobu's smile turned into a smirk as the rays of the sun shone with her proud eyes. She couldn't even believe she fell asleep just after finding out what she had been looking for.

"I might've found a way to help [Y/N]"

The first time [Y/N] called her master by his name was a day that he would never forget.

He had stayed next to her through her hospitalization and refused to move unless she begged him to eat, sleep, take a bath and change clothes. He simply didn't want to miss any of the little time he had left with her. He became more desperate for her recovery, deciding that it was not worth living in a world in which he couldn't see her smile, hear her voice or watch her over the top reactions.

He was good at hiding how flustered he was though.

The point is that they would stay inside her room playing games or talking for hours, which certainly wasn't good for the poor boy's heart. By this point, he wasn't used to the feeling of loving to that extent, and would often blush at the smallest things, like when he let her win at some board games and she would hug him out of pure joy, or simply smile or even hold hands.

He was sure that his heart would explote sooner of later, but it was worth it.

"Ah, Tokito-sama..."

Muichiro looked up, finding his lover's thoughtful eyes set over him. He straightened himself and switched his attention to her as soon as she opened her mouth to speak, as he always did.

A sweat bead slid down his face as his brows slightly knitted in subtle worry. "Does your chest hurt again? Should I call Shinobu?"

"No, no! It's nothing like that!" she exclaimed, waving her hands in a denying manner. "I've just noticed that even though we're clearly future husband and wife, I still refer to you respectfully. Should I still refer to you as Tokito-sama?"

Good question.

He was used to hearing her refer to him respectfully. His name always sounded sweeter when it fell from her lips. But it's true that he would be happier if she addressed him by his first name.

"What would make you happier?" he asked, to which [Y/N]'s whole self began glowing out of delight.

"I'd love to call you by your name if that's okay, master!" she said excitedly, unconsciously filling the room with the warm and flowery aura of spring in the middle of summer. He nodded, giving her permission to do so. She promptly became a little embarrassed of actually calling him like that, but she really wanted to at least try. "T-Then let's keep playing, Muichiro"

Muichiro's mind became a complete blank space.

His cheeks flushed red, feeling so hot that he hurried to look away and hide it with his hands.

He hated the fact that he didn't bring a recorder with him.

"Why do I have such a cute girlfriend? I'm gonna die before her at this rate. I swear."

He felt like he could now die in peace.

...

That last quote hits different with the situation we're having and the actual demon slayer manga. Haha.