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 16: After the lullaby, Nezuko's finally properly resting and the medicine's doing it's job. Tanjiro can finally rest again...but he has another strange dream.

After cradling the girl for a short while, Tamayo cleaned up the murky fluid mess Nezuko spit up on the bed earlier then tucked the small sickly girl into the now cleaned up sheets. Nezuko was now in a much needed deep slumber. Her fever was still present, but it was starting to deteriorate from its dangerous state. She was more stable than any other time she was asleep. The medicine must have been working.

A small washcloth was placed upon her forehead to cool her down and while she was unmuzzled Tamayo placed a glass thermometer in her mouth under her tongue to read her current temperature. There were still remnants of tears drying in her puffy closed eyes from her breakdown earlier. She was lightly snoring as Tamayo took the thermometer out to read the number. It read 106.2 degrees Fahrenheit. But to a demon, this apparently wasn't a serious fever.

While she calmly slept Tamayo found another piece of bamboo close by and some fabric so she could be muzzled again. As Tamayo worked on making her a new muzzle, Tanjiro watched tiredly as he was about to pass out himself. It's been a long and exhausting few days, but he was just happy Nezuko was finally showing signs of recovery. Beside him, Yushiro was too busy daydreaming about Tamayo's beautiful voice that he just heard. He was so writing this in is Tamayo diary tonight.

"Tanjiro are you alright?" Tamayo asked as she walked toward him.

"I'm okay…just exhausted…this was very hard…on both of us…" he held his throbbing head.

Tamayo placed her hand on his forehead. "I can tell. Yushiro please get Tanjiro some asprin from the human medicine."

He was a bit distracted but as Tamayo called him instructing him a second time. He answered with "Yes Milady!" before he went over to the medicine shelf then leaving to get the water.

"So is Nezuko going to be alright?" Tanjiro asked the doctor.

"Yes, she will be okay. But she was in a critical state when you brought her here. If you hadn't come when you did, she wouldn't have made it through another night."

"I thought so… After she ran away from the demon slayer corps, she got worse and started coughing up blood. I was really scared she wouldn't make it…" Tanjiro said almost on the verge of tears.

"She was in worse shape than I thought but you just made it and she should pull through okay now." Tamayo stated. "I'm glad you were able to come here."

"Do you know what exactly type of virus she had?" Tanjiro asked curiously.

"Because us demons usually never fall ill and mostly just get hurt, we don't really come up with names for it. But we'll just say its similar to a severe human case of influenza that may have graduated to pneumonia." The doctor replied still putting the new muzzle together.

"That explains why her fever was so high." Tanjiro said looking to Nezuko asleep in the bed.

Pneumonia... That's the same illness that my father was subjected to.

Tanjiro shook his head before looking back to Tamayo. "I was wondering... Do demons get higher fevers than humans?"

"Yes, demon biology works differently than a human. They're more advanced so in order for a fever to strike a demon down, it can raise much higher than usual. A normal fever for a human is nothing to a demon."

"I see. So even with a normal fever, Nezuko would be, okay?"

"I believe so. But it is still wise to let her rest if this ever happens. I knew she was a unique demon with a rare circumstance from her blood, and I suppose this includes being prone to illness as well. It at least proves she still has humane qualities. Most demons don't fall ill at all. This was a rare case. I'm glad I was experimenting in medicines for demons at the time while looking into the cure for her humanity."

"So if it started as influenza...do you think it could it have been the rain?" Tanjiro asked.

"I don't know for sure but possibly." She replied. "Best to take care and cover up next time it rains on a mission."

Tanjiro nodded before Tamayo just finished the new muzzle for Nezuko. "There we go. All done." She stood up and gently placed the newly made bamboo muzzle to Nezuko's mouth and tied it behind her neck. Nezuko didn't budge at all. She was completely knocked out.

"Really... I can't thank you enough Miss Tamayo." Tanjiro bowed to the doctor. "And I'm sorry if we may have put you at risk again by doing this…"

"It's alright Tanjiro. We cannot let Nezuko die. She's our only hope to finding a cure for demons after all so I was willing to take the risk. But we will have to move again to be safe…"

"She really could've died from this!?" Tanjiro exclaimed in shock.

"Possibly." Tamayo said. "But she will be okay. You brought her just in time as I said. Her condition is now slowly stabilizing. The medicine should do its work overnight."

"Thank goodness…" Tanjiro said as he placed his hand to Nezuko's head and pet her as she slept. Now knowing he was safe since she had a new muzzle.

Yushiro returned to the room with the cup of water for Tanjiro to drink and handed him the asprin from the medicine cabinet.

"Thank you." He responded taking both the items as he dropped the asprin tablet in his mouth and downed the water.

"Chachamaru can lead you back to where you first were whenever you leave. And you best do it at night since you forgot the box to contain your sister." Yushiro responded as the cat appeared like clockwork with another meow.

Tanjiro decided to move closer to the cat and give the calico some pets and attention causing the cat to purr.

"Thank you for your help, Chachamaru." He said smiling continuing to pet the cat.

"We should wait for Nezuko's temperature to go down a bit more before you leave." Tamayo stated. "Its still too high right now to not be a risk to the chilly night air."

"I understand." Tanjiro responded. He wanted so badly to take a small nap.

"Please make yourself at home in the meantime. I'll continue to stay with Nezuko. I may take a small sample of her blood too while she's here, as it may have had changes I can look into for further research on the cure."

"Sure… Go ahead…" Tanjiro said before he wobbly got up leaving the clinic and headed for another room. He laid down on a comfortable pillow of Tamayo's living room quarters and closed his eyes for a little bit of shuteye.

As Tanjiro slept, he was back in the same blank space he was in before the day Nezuko first got ill. It was dark and desolate as it was the first time.

"Am I in Nezuko's mind again?" Tanjiro asked to himself as he slowly wandered.

He didn't hear any pained cries for help from Nezuko this time though.

He decided to try to find where she was this time to see if she was doing better. The walking seemed endless, but he could see a small light in the distance.

He ran towards it for a while to find himself in the same area. But this time there was no red-hot thorny vines and a cage containing his sister's body. This time he saw a small green pool of water and some small lights coming from it. It felt calm and serene and there was a white figure in the center of the water.

It was Nezuko's ghostly spirit. It wasn't in the fetal position and wasn't in pain. She looked like she was at peace bathing in this spirit-like pool of water. Her eyes closed her hands together and her long hair surrounding her white bare body.

Tanjiro walked closer to her and tried to call her name out again to see if she could hear him this time.

"Nezuko…? Nezuko!" Tanjiro called out to the ghostly figure.

The spirit slowly opened her familiar gentle pink eyes and looked over to Tanjiro. She was able to hear him this time. She closed her eyes and slowly got out of the water then flew toward Tanjiro.

Tanjiro was a little nervous, but he knew his sister wouldn't harm him.

Once she was close enough and looked at Tanjiro, she smiled at him closing her eyes as she flew away into the void disappearing.

Tanjiro was about to wake up again, but he swore he could hear something before he was fully conscious.

"Big Brother…. It doesn't hurt anymore… You saved me… Thank you."

Tanjiro woke up feeling fully refreshed. Wiping his eyes, he quietly began to speak to himself about what he just saw. "That dream… That area… Could that have been… Nezuko's interpretation of the process of being healed? A healing spring to soothe a pained spirit…it makes sense…"

He got up feeling like the spring may have healed him as well. Maybe that was Nezuko giving him the strength he needed to carry them both back to the corps before the sun came up.

Tamayo walked into the room carrying Nezuko.

"Tanjiro. She's stable enough for travel now."

"Okay I understand." He responded getting up and walking over to Tamayo to lift his sister from her arms and into his. The small, muzzled demon was sound asleep. Tanjiro smiled at her. He felt a lot better now. That dream and the ease of Nezuko getting better gave him the strength to press onward.

He then wrapped the front of his haori around her to keep her warm as he held her small body.

"Okay Nezuko. Let's go home." he said smiling looking down at her.

…mmm…." Nezuko very quietly responded back in her sleep.

"Tanjiro, wait." Tamayo said walking towards him holding something.

"What is it?" Tanjiro said.

Tamayo hands him a small scroll and a small bag of spare ingredients.

"If this ever happens to her again, this is the contents for the medicine I gave to her. Give it to whoever is in charge of medicine in the demon slayer corps."

Tanjiro grabbed it and smiled.

"Thank you so much Tamayo!" he smiled now thinking Shinobu could make the medicine and help Nezuko if it happened again. Shinobu looked so down that she couldn't help her before.

"Alright let's get you outta here. We have to move locations again soon" Yushiro stated pushing Tanjiro to the door.

Soon they were outside the clinic and Tanjiro bowed his head to say his final farewells and gratitude to Tamayo and Yushiro. Chachamaru then walked outside the barrier with Tanjiro following.

"Okay I'm ready when you are Chachamaru." Tanjiro said looking down at the cat as it looked back up at him.

The cat then dashed away with Tanjiro following not far behind.

Chapter 16 done! Nezuko finally got her cure and is getting better. Time for them to return to the estate.