***

They passed through the corridor and headed up the stairs. The east wing of the second floor of the Headquarters was for the servants' bedrooms.

Barbara was currently staying there.

Yomite was not 100% sure yet, but there was a chance he might be of some help. Barbara didn't have a fever, which was a good sign to figure out the diagnosis.

Fundamentally, fever was the body's instinctual defense in order to oppose the toxins inside the body.

That much he knew, and so did anyone else.

Which was to say, for the body temperature to not rise for fighting the disease's toxin, it either meant that the body refused to recover or the body function to resist itself wasn't working.

(If her body temperature is falling...Coupled with every symptom that was mentioned to me earlier, then the highest known possibility about an illness I have knowledge of...would be that Barbara is suffering from...Cholera. The same illness...my mother succumbed to. What are the odds...)

He wryly smiled.

Cholera.

It was a disease most people have heard of. It was also a disease even more people probably didn't understand.

At this point, Yomite was just guessing. It could be a new, never-before-seen illness, but it could also be Cholera, and if it was the latter, then she still had a chance of survival.

But if it was the former...there was no way to treat something you don't know how to treat...

He turned to Jean and said, "I was thinking about which illness it is and I think I know. It might be Cholera."

"...And, what's this... Cholera?"

Jean tilted her head at the disease name that she had never heard about. For Jean, it was only natural she would know all kinds of things.

She was studying about everything ever since she was little so that she could become the perfect leader of Knights of Favonius and protect Mondstadt from any obstacles, so naturally, she had to learn about viruses and Illnesses too.

Something like this wasn't completely new territory to her, but the name didn't ring a bell no matter how hard she tried to remember.

In South Africa, Cholera was one of the main reasons the population had declined back in the days.

Over hundreds of thousands of people have died from it, including his mother.

Well, it was normal Jean didn't recognize it, as, in the end, Cholera was the name of the disease from South Africa. From Earth. It wasn't the name circulating in this world.

At least, not yet...

"It's a powerful contagious disease. Due to it causing fierce diarrhea to the patient, many people died from the dehydration that it caused. Because the body loses a lot of water so abruptly, even a young person will dry up completely, looking like an old person with wrinkled skin."

"So it's that...That is exactly her condition...Please...can Barbara be saved? I will do anything..." Jean pleaded.

"It's hard to tell if I can help...There are various types of this disease. I don't know which of them Barbara's Cholera falls under. Even so, the chance for her to be saved shouldn't be low, but I am not sure..."

Jean's blood almost froze in her veins, "...I see... It's fine...If you aren't able to help... it's not your fault..."

Yomite sighed and flicked her forehead.

"Ah..." Jean didn't expect the sudden attack as she was too distracted by her negative thoughts.

"I didn't say I would give up on her. You said you would do anything, right? Then how about a date? If I manage to save your sister?"

Yomite proposed as he winked at her. His voice was calm and soothing, trying to comfort her and make her relax as much as possible.

All of this was of course, just to make her think about something else.

"A...Date...? Alright...I...I can do that much...If you save my sister then I will take a day off for you, no...even a week..." She accepted the confusing request without hesitation.

"Wait...week is a bit too much...maybe a couple of days...No...A day should be enough, right? I am sorry but there is still so much work for me to do and it's piling up..." She was fidgeting while thinking about her schedule.

(Workaholic to the core, huh.)

He wryly smiled once more.

Paimon observed the situation and concluded, "What a womanizer...Paimon feels like you are in danger as well so be on guard with the Rude Dragon Tattoo!"

Lumine shook her head and replied, "I can tell he feels no attraction towards me whatsoever. You can kind of tell who he takes a liking to just by looking into his eyes and distinguishing his facial expressions."

She didn't know whether she should feel happy he wasn't attracted to her, or disappointed because she lacked women's charm.

Paimon looked around to see if anyone heard what she just said, and whispered, "Sorry, but Paimon thinks you sounded like a creep just now...Does that mean you are usually paying a really close attention to him then~?"

"I'm not."

"Re~ally?"

Paimon wasn't convinced.

"I'm not."

In case the cholera wasn't treated, the death rate would be 50% at the lowest and 90% at the highest.

However, putting it another way, humans could recover from this sickness with more than a ten percent chance even if they only relied on their own natural recovery.

However, because this disease was highly contagious, many of the isolated patients were placed in an area with bad sanitary conditions and died.

There was even a case in the past where a country was ruined because of the pandemic's outbreak.

When cholera was prevalent in western Japan in the closing years of the Edo period, it was said that the number of the deceased reached a hundred thousand, which was similar to the South African record.

As expected, even Yomite couldn't make an estimate on how far this disease had spread within the world of Teyvat, or Mondstadt itself.