The Demon King Seems to Conquer the World 17 (Self Edited) – Utility



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After the 10th birthday, the entrance ceremony of the school of Knights was approaching. Although there was no entrance examination, I was pushed to be here at the critical moment.

Leaving that aside, I should talk about Rook.

Satsuki said that Rook’s life wouldn’t change, but eventually, his life changed dramatically.

Certainly, it would have been possible to continue running the ranch as before if he abandoned everything, but Rook, who had a strong sense of responsibility, couldn’t do so. These days, he entrusted most of the work to other people, and he was doing his job as the chief of the household.

Meeting with the Knight subordinates, having talks, addressing appropriate posting and rebuilding the order of the Knights. Still, he didn’t intend to quit the ranch management. He continued doing it as a sideline job. However, when he went to do the ranch, he commuted with his personal Eagle King.

While being a rancher, he didn’t own any Eagle King.

When needed, he rode the Eagle King which hadn’t been sold yet. Since keeping it cost him money, it was wasteful to keep an Eagle which wasn’t an article for sale. Now that wasn’t the case. It was finally the first time in his life to own a personal Eagle King.

Suzuya seemed to be adapting normally. She was living at her own pace, while gardening, cooking and creating a good relationships with the maids. That might be thanks to her personality.

In social circles, her body was weak and it was difficult to participate in events. She had a weak body because of hard labor when she was young. Of course, Satsuki participating in the events instead of Suzuya.

As a result, the burden had been reduced considerably as Suzuya didn’t need to participate in unless it was important events that she must attend by all means.



“I’m sorry, but I’m not going to the ranch tomorrow.” (Rook)

That day, Rook told me that during the dinner.

This wasn’t unusual. There should be any sudden change of plans because Rook’s scheduled had been filled up for a month, but still, I couldn’t predict our old relatives died. Therefore, funerals were mainly to be a sudden change of schedule.

Anyhow, that was unfortunate. For me, simple labor and practiced with birds on the ranch had become the most enjoyable entertainment.

“Is it because someone’s funeral?” (Yuri)

“No, that’s not it.” (Rook)

It seemed to be different.

“So, what then?” (Yuri)

“A disease has spread. In the town of the south.” (Yuri)

Plague. It sounded dangerous.

“It seems to be smallpox disease.” (Rook) (TLN: I was trying to find a different name for smallpox, but I couldn’t.)

‘I see. I’ve heard about it.’

“Isn’t it better not to go there?” (Yuri)

When I said that…

“I can’t do that. Especially when people are in trouble.” (Rook)

…he told me so.

“But, you’ll be in trouble if you get infected.” (Yuri)

“You are worrywart. It won’t spread that easily.” (Rook)

‘How’s that so? If he is referring to the rule of thumb, that’s still fine. Anyhow, that is a judgment without a scientific basis.’

“Well then, I’m going too.” (Yuri)

“Eh, do you want to go as well?” (Rook)

“It would be nice if it doesn’t spread that easily.” (Yuri)

“But…” (Rook)

He was reluctant.

“I would like to see what the disease looks like. Please.” (Yuri)

“I got it. But, do as I say.” (Rook)

‘That is my line!’

I wanted to shout that, but I had to suppress my mouth.



The next day, we went out by riding an Eagle King from the morning. Recently, I was allowed to hold the rein as a practice during the cruise flight.

The territory of Hou’s Household was vast.

It seemed to spread about 100 KM, but moving through it was considerably difficult. There was no GPS in this world. On the contrary, there was no decent map or compass that could be used in the air.

So, we would fly by intuition while looking at the ground terrain. In other words, we couldn’t reach the destination unless we knew the terrain of the ground in detail. If we flew in hurry, we would get lost.

We were flying for about one hour. We managed to get to the destination.

Since the city was a good landmark, the terrain was basically based on a city, so I remembered that. If I remembered the terrains that directly connected to the major cities, there should be no problem at all. It was like an airway.

I gave the rein to Rook, because I didn’t know the way from the city. Rook had taken a course toward the west and was flying for a while. In the meantime, I saw dark smoke rising in the sky. It was a beacon.

When I returned the rein to Rook, the Eagle King looked down and started to descend.

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According to some books, the smallpox was the disease that was brought from the Kura country when there was still Shantilla Great Empire.

There was no effective treatment once people were inflicted, and the probability of dying was 50%. Speaking of the knowledge, I had it until that extent.

Before we got into the village where smallpox disease was prevalent, I gave Rook three sheets of long cloth like a washcloth.

“Here you go.” (Yuri)

When I said that…

“What is this?” (Rook)

…he said while in doubt.

“Please cover your mouth and nose.” (Yuri)

I covered my mouth and nose with a towel.

It became harder to breath, but I could still breath.

“Why?” (Rook)

“That is for disease prevention.” (Yuri)

I said it and I did what I said. Such a common sense didn’t apply in this world.

They didn’t know the existence of pathogens or viruses. They were thinking that it was a poison that blew from the ground and that was the cause of the disease. Well, they thought that it was only contagious for a while. That was the extent of their understanding.

‘How should I explain this?’

“Anyhow, this way can greatly reduce the possibility of disease transfer.” (Yuri)

“But, that’s not cool.” (Rook)

‘He doesn’t like it.’

‘It is probably because the dignity of a feudal Lord. Oi, Lord-sama. Wear the mask in that way, or you’ll get the disease, you know. As expected, it’s not good for public appearance.’

‘I mean that kind of feeling.’

“If Otou-san comes home with the disease, it might be transmitted to nursing mothers, and it might be transmitted to Satsuki-Obaachan and me. Then, the whole family is destroyed and that is the end of the household. I think it’s not cool to take that risk.” (Yuri)

When I told that seriously…

“G-got it… I will put it on…” (Rook)

Then, Rook reluctantly put on a mask.

‘Good, good.’



After that, we walked into the village.

“There are sick people who don’t have anyone to take care of them here.” (??)

The building where the guide explained was something like a town hall or a meeting hall. He opened the door.

When we went inside, the smell was overwhelming.

The moment I saw the sick people lying in a sleeping place with a line bag, which I couldn’t say a bed, I wanted to cover my eyes.

Their face and arms were covered with blisters about the size of their fingertips. Perhaps, it had spread to the body as well.

The degree varied depending on the patients, but in the case of patients who were in a severe condition, their arms were covered with blisters from the face, and it was more difficult to find healthy skin. They seemed to be uniformly treated with high fever.

‘This is bad.’

There were also some patients whose skins had been scratched and their face was covered in blood.

“Otou-san, please don’t touch the sick people absolutely.” (Yuri)

It sounded so bad if that heard by the sick people, so I whispered that to him. Ideally, I wanted to get Rook out of this building right away.

“Got it.” (Rook)

Rook said so while looked upset. Indeed, the disease would probably spread if we touched the sick people.

“But, it’s terrible…” (Rook)

Rook looked around the room and came back while observing the sick people. I didn’t feel like looking at them. It was like watching a baby played innocently with a dagger that had just returned back from sharpening.

When he finished watching around and came back, I grabbed Rook’s hand.

“O-oi. Wait a second.” (Rook)

I pulled him all the way to the door.

“Please open the door.” (Yuri)

When I said that, the guide had a slightly suspicious look. It seemed that he was going to say that if I was in a hurry, I should open it myself.

I couldn’t do that. The doorknob should be covered with pus in the blisters. From my point of view, it was like a deadly poison.

“Please open the door quickly.” (Yuri)

When I said that again, the guide opened the door. We hurried to get out of the building.

“What the… what’s wrong?” (Rook)

“If we stay in that room, Otou-san will get sick.” (Yuri)

“That’s an exaggeration.” (Rook)

Rook looked at me as if he was looking at his troubled son.

“I’m not exaggerating.” (Yuri)

I was aware of the disease. It was too similar to smallpox.

Smallpox was a disease caused by smallpox virus. People would become ill after a half month of incubation period from infection. Then, the blisters that contained puss all over the body would come up. It wasn’t only on the body surface, but the same symptoms appeared in the viscera, and it would start to cause inflammation from the inside and the outside.

Then, the people would seen to have high fever near forty degrees, and that lasted for a few days. In the meantime, those who didn’t have the resilience would die.

It was fortunate that they would be able to eradicate the virus from the body in a few days, but the mortality rate was about 25%. That was considerably high mortality rate. Since 25% was the average value, the mortality rate would go up if this happened in a community where there were fewer things to eat due to bad harvests and population resilience was declining. That was in the case of human. Hence, it might be worse for Shanti.

In addition to being highly contagious, smallpox was bothersome because of its symptoms. Since sick people had blisters with pus inside, the pus and the part of the skin that came out would remain in the surroundings. Of course, it contained plenty of smallpox virus and it was infectious.

Furthermore, the smallpox virus was very strong, and unlike HIV, which inactivated the moment it left the body, this virus survived in the pieces of skin, and it didn’t became inactive for nearly a year.

Then, the pus and the part of skin tissue adhered to human hands, back of shoes, fibers of clothes and others. After that, the infection spread rapidly. It was a very troublesome disease, with a high level of infection and lethality, combined with a variety of characteristics.

“I got it. I really got it, you know. What should I do?” (Rook)

“Let’s go home now.” (Yuri)

When I said that…

“I can’t do that.” (Rook)

…he replied that way.


“I have a duty as a Lord. I have to save the people here. I can’t run away and do nothing just because I am afraid of the disease.” (Rook)

‘Dear me. That’s reasonable.’

I really wanted to sigh.

“So, what are you going to do?” (Yuri)

“That is… gather people from around, open the storehouses, and give food…” (Rook)

“It’s good to give them food, but the disease will spread if you gather people. The Lord’s job is not to help the 100 people here and let 1000 get sick, but the job is to let the number remain as 100.” (Yuri)

“It may be surely so. But then, what should I do? Are you telling me to wait for the people here to die? As a Lord, I…” (Rook)

He became serious out of nowhere.

“Please listen to me. If you gather people, make sure they don’t get infected. There is a way to make people not infected with this disease for a certain period of time.” (Yuri)

“…What?” (Rook)

“Let’s find farmers who have cows in this village. It is good to have farmers who milk a lot and distribute it to the village.” (Yuri)

“What, you didn’t want to go home?” (Rook)

“I think it is best to let other people check after going home, but since this can be done quickly, we should go now.” (Yuri)

When I thought about it, even if people were infected, there would still time if they were given the vaccine. The reason why the symptoms didn’t become apparent because people had antibodies before the smallpox virus multiplied in the body.

“I got it. Shall we go?” (Rook)

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When we arrived at the farm that we heard from the guide, they were living perfectly normal as I expected. They were scared of the infection, but they had no smallpox patient. We thanked them, and then, they left.

“As I expected, they are fine.” (Yuri)

“Isn’t it a coincidence?” (Rook)

Rook was skeptical.

“That’s not it. All people of this house are not infected. Let’s squeeze the udders together with everyone.” (Yuri)

“What do you mean?” (Rook)

“How should I explain this… there is the same kind of disease that cows suffer from. The cows have the same symptoms as the disease. However, the symptom is the extent to which some blisters can appear around the udders. The cows never die from that. So, the disease is transmitted from the cows to human, but even if it spreads, the symptoms are light. One or two blisters may appear, which can cause the body to become slightly sluggish, but it doesn’t affect the daily life. These people got sick while milking sick cows.” (Yuri)

“I don’t understand. Why they don’t get sick?” (Rook)

“That is… well, if I have to say, the body has experience of fighting similar enemies, so I’m sure that the body won’t lose if it gets infected by the fatal disease, right? If you are fighting an expert of spear art, and you have previously fought a weaker opponent of the same school, you can proceed in an advantageous way. It’s the same analogy.” (Yuri)

Actually, it was different, but that would be easier for Rook to understand if such an analogy was given.

In Japan, the disease that cows suffered was called cowpox. Vaccination using cowpox was established early as a preventative measure against smallpox. Cowpox was a virus that was closely related to smallpox. It could be transmitted to human, but there was little harm.

Although a primordial vaccine against smallpox was called smallpox vaccination. In other words, once human were infected with cowpox, which was attenuated species of smallpox, they would create immunity.

Smallpox was a deadly infectious disease, but unlike HIV and influenza, vaccination was a very effective disease. If people get immunized with vaccination, they would never get smallpox until the immunity was lost. Even if it occurred, the infection could be minimized by immunizing all the surrounding population.

“After all, I don’t really know. I have never heard of that before.” (Rook)

“Is that so? But there is such a talk.” (Yuri)

“So, what should I do?” (Rook)

“Look for cows with blister on its udders. Then, crush the blister with a needle or something. After that, apply the contents to the person’s arm or somewhere and scratch it so that a little blood may come from above the skin. If the disease is transmitted well, they will get some reaction. That’s it.” (Yuri)

“I see… I got it. If you say so, shall we do that?” (Rook)

It seemed that he finally got out from being uneasy.

I might spell it uneasy, but I wondered how many adults willing to do it if a ten years old child said such a thing. If Rook didn’t believe me, he must have been laughing by now.

Even if adults trusted me, if they weren’t good ones, they wouldn’t have listened to me.

‘I really appreciate it, Otou-san.’

“Alright, let’s go home for today.” (Rook)



When I returned home by riding an Eagle King, I keep a distance from people, took off all my shoes and clothes, put them in a bag, washed the exposed face and hands with distilled alcohol, took a bath and put on new clothes. Rook also had a hard time smiling, but he went along with me.

I felt that my stock share had fallen a little by this time, but it couldn’t be helped. The bag was put deep inside if a storehouse, and it was decided to remain in quarantine for more than two years.

Two days later, cows infected with cowpox were discovered, and all the sick people in that village were vaccinated. The village was to be isolated until the infection settled down. I thought that we should be alright, but since Rook and I were both late, we went there to get vaccinated. Since this was the fourth day, it should be fine. The symptoms could be suppressed considerably even if it developed.

I was worried about the effects when it was about the vaccination, but most of the people who got vaccinated avoided the infection. It seemed that the effect was as expected. There were very few people who had been infected, but it was probably the failure of getting vaccinated.

Although I was relieved that the smallpox vaccination project, which had become a bit of large scale, had succeeded, I could feel that I was having a slight cold.



  • I am not a medical doctor, so if I made any mistakes in this chapter, please let me know.
  • Don’t click the Wiki link if you have soft heart, I suppose. However, if you still want to learn more about smallpox, you can click here.

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6 thoughts on “The Demon King Seems to Conquer the World 17 (Self Edited) – Utility

  1. lar

    Thx for the chapter!
    At first tough the demon king would be the enemy, but maybe he is going to become it?
    It seems not many read it but i am enyoing plentifull


  2. Halmista

    Holy cow! He just introduced vaccination in a medieval-kind world at the age of 10. And I just love how his father just went with his words. He completely obeyed after getting his questions answered. His full trust towards Yuri is heartwarming. I want to see the reactions of everyone once they learn about Yuri’s accomplishments.


  3. OneTrueGriffith

    Unrealistic nonsense. Just because it’s a low fantasy setting doesn’t mean a story is devoid of reality, especially the reality of the world’s own rules. In a world where women aren’t taught shougi, and even the head of a house’s daughter isn’t given books, a small boy can just say anything and be treated amicably without tension, confusion or fear?

    This world is hollow and the writer has failed to make a living, breathing world. Typical isekai fanfic trash. “Look at me, I’m introducing algebra and telling you the earth revolves around the sun, and curing plague… all out in the open with no consequence!” Galileo was imprisoned by the POPE for talking about the sun. LOL. Get real with this Mary Stu garbage.


    1. bayabusco Post author

      I’m not sure how did you miss it. The daughter had been taught by the mother, who studied in the school of Liberal Arts, before she met Yuri. Realistically speaking, there should be a lot of books in their house.

      If you say about Galileo being prisoned because he was spreading his knowledge, there is still loophole where the boy wouldn’t face consequences. What if the 9yo girl he taught never told anyone what she had learned (remember, Yuri never taught anyone except Syamu). Even if she told anyone, people wouldn’t take her seriously.

      In this world, they play togi or Chinese chess rather than shougi. It is popular for all ages in this world. So, I’m not sure where did you get the notion children in this novel didn’t learn to play togi.

      Liked by 1 person


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