Author's Note: Hiii its me again! I'm back after a while with a new story! This one's based Demon Slayer Kimetsu No Yaiba. I recently got into the series and I fell in love with it. But I noticed there were NO sickfics of it on here. So to my disappointment I thought, okay time to take matters into my own hands here! And after a few months of thinking, I got this interesting idea. And I'm aware that the manga confirms that demons can't get sick, but hey Nezuko's a unique demon so maybe she's an exception) It'll be a bit more intense than my usual fluffy fics, this one has a bit of a story arc to it. As usual I hope you enjoy and I hope I do these characters justice or get their personalities right in the writing because I've only been into this series for a couple months.

This may also be my longest fic yet. I have some plans for this one c:

Chapter 2: The boys make it to the inn and things start getting bad when Zenitsu hears something strange in the middle of the night.

When the three demon slayers made it to the inn it did indeed have the wisteria crest on it. The three boys were greeted by another old lady, seeming to be different from the previous one but similar enough to make Zenistu freak out over her ghoulish appearance calling her a monster and ghost causing Tanjiro to shut him up by banging him on the head repeatedly. As the trio went inside, they were treated to warm new robes after they dried themselves up and Tanjiro set Nezuko's box down in the corner of the room they were going to stay in. They all received a nice meal which everyone scarfed down, Inosuke once again stealing food from Tanjiro to try to get him mad, but to no avail. And then before long they were all ready for bed. They talked for a bit before everyone collectively fell asleep warm and dry. There were no signs of any of them falling ill.

Not any of the boys anyway.

Zenitsu awakened in the middle of the night to use the bathroom like he always does. Walking to the facility room and back trying to not wake his friends up. Waking up Inosuke seemed impossible anyway with the loud snoring. He was often afraid to go alone, but he managed to make it to the room by himself, trembling slightly along the way.

After he came back and was about to lay back down on his futon, his ears caught something causing him to jolt awake more. Zenitsu was known to have good hearing, better than most people hearing many things not any other people could hear. Trying to ignore Inosuke's loud snoring, he concentrated and tried to find where the other noise was. It didn't take long before he found it. It sounded like…deep abnormal breathing.

He immediately entered panic mode. This sounded somewhat like a hungry monster. Was a demon outside the room? Was it planning to eat them while they slept?! He trembled violently, tears streaming down his eyes whimpering slightly. He really wanted to wake Tanjiro up for this but decided not to after all of the unnecessary times he woke him up before feeling guilty. He had to face this on his own. Trembling every step of the way he opened the sliding door to the outside of the room and checked his surroundings carefully. Looking for anything that seemed out of the ordinary. There was nothing but a calm peaceful yet humid night sky when the rain stopped. He sighed in relief and noticed the sound got quieter as he left the room. He then shut the door and looked back with a face of horror whimpering slightly.

DID THIS MEAN THE DEMON WAS IN THEIR ROOM?!

IN THE BUILDING?!

Zenitsu tried to calm down but he was trembling and crying the whole time he looked. He looked all over the room. Nothing. He looked around the mansion trying to be quiet. Still nothing. The sound would disappear if he ever left their room. So, it was in their room. He whined and closed his eye and focused on where the noise was coming from. He then realized the source of the sound. It was coming from the corner of the room, in Nezuko's box. He then calmed down a bit.

Oh of course, there's a demon in the room. His beloved angel sweetheart Nezuko-chan sleeping in the wooden box in the corner of the room. By far the cutest demon in the world. He sighed in relief saying to himself "Oh, it's just Nezuko-chan." But then before he slid back into his futon to go back to sleep, his ears perked again to the sounds. Then he crawled over to the box he put his ear on it to listen in more. The noises were louder. The sounds were clearer. It was loud, labored, muffled breathing with occasional soft moaning. Something wasn't right. Nezuko didn't ever do this, she was often so quiet while asleep. Like a little angel, not a sound. What happened? Why are these sounds coming from her box? What was wrong with her?

Zenitsu reached to open the box as he knew it was unlocked, but he was a little nervous at first because he never opened the box while she slept before. Cute as she was, she was still a demon and might get mad if he bothered her. He then put his hand back, he couldn't do it. He wanted to help his beloved, but he was too scared to try. The noises continued to bother him though. There was no other option, he had to wake Tanjiro up. He went over to the futon where the redheaded water breathing slayer was calmly softly snoring. He shook his shoulder gently.

"Tanjiro… Wake up. Please wake up…!" Zenitsu called quietly.

Tanjiro groaned a bit and brushed off the calls.

"Tanjiro please…! It's an emergency…!" he called again a bit louder.

"Nn… Zenistu for crying out loud… What is it this time…?" he said sleepily looking up at him, one eye open his hand wiping the other.

"Sorry to wake you but I swear it's a real issue…" he said feeling guilt for all the other times he woke him up. But was sure this one was 100% necessary.

"What is it…?" Tanjiro responded still sleepy and not paying much attention.

Zenistu took a few second to collect his words before he spoke up again.

"I… I think…" he began.

"Yes…?" Tanjiro replied.

"I think… I think something's wrong with Nezuko-chan!" he finally said a bit loudly.

Those words caused Tanjiro's eyes to snap right open. He didn't even respond, as he quickly crawled over to Nezuko's box and opened it. He saw his sister curled up, eyes clenched shut, shivering, and breathing heavily through her bamboo muzzle. Heat emitted from her body and her face was drenched in sweat. She looked horrible and uncomfortable.

"N-Nezuko! What happened to you?!" he frantically said before he tried to lift her small body. "Are you okay?!"

Nezuko let out a tiny but audible moan as he lifted her and cradled her like a small child. Though that was exactly what it looked like with her small size not changing due to being unconscious. She looked as big as a fully grown toddler just reaching their child years.

"No… She's burning up…" Tanjiro said softly touching his sister's forehead.

"Uwaaahhh, I knew it! I had a feeling she wasn't doing well with those sounds I heard…!" Zenistu said looking down at Nezuko with pure worry in his eyes already crying.

Tanjiro looked up at Zenitsu and sighed. "Hey now, try to calm down, okay? That's not helping you know." He said in a bit of a scolding tone before looking back down as his sister.

"I-I'm sorry…" Zenitsu said trying to wipe away his tears.

Tanjiro looked Nezuko over again. She was unconscious and her eyes wouldn't open. Her body was shaking uncontrollably, and she was suffering from a high fever. It was scarily high. Unlike anything Tanjiro ever felt before. He immediately got concerned.

"This is bad. She's way too hot. This isn't a normal body temperature." Tanjiro said feeling every other part of his sister's body. But he remembered she wasn't human anymore. "But I didn't think demons even got sick…"

"Could it have been from the rain? Maybe her box got too soaked…" Zenitsu suggested.

"I don't know… But I'm worried. I think we'll have to cancel this mission or put it on hold. She can't fight like this and needs to rest."

Before anything else could be said Nezuko began violently spazzing in Tanjiro's arms, flailing her arms around, growling and moaning. The high fever was confusing her. She was starting to lose control of herself.

Chapter 2 done! Poor Nezuko. Being sick for the first time is probably very frightening. Especially if you're a demon and have no idea what's going on with you.