The Demon King Seems to Conquer the World 57 (Self Edited) – Celestial Navigation


Celestial Navigation


The three of us left Eisa-Sensei’s preparation room and went to the headquarters right in front of the secondary residence.

“I guess you didn’t know the ritual, did you?” (Harold)

When I entered the headquarters, Harold spoke as I remembered it.

“Is there such an absurd thing? Who will leave your Sensei’s life in your hand?” (Yuri)

‘No, seriously.’

“…” (Harold)

“At best, I tell you before you betray me. There’s a possibility I can help Sensei.” (Yuri)

‘I supposed it would be fine if Harold betrayed me since it would be difficult for Eisa-Sensei to know it before me.’

“How can you help?” (Harold)

“I’ll hire people to monitor her all the time, and if she goes into the forest, she will be restrained. But… In that case, I may have to force her to eat.” (Yuri)

‘I think that there is a possibility that Eisa-Sensei will fast and die. In that case, if I make her drink something like porridge even while she is asleep. So I will be able to help Eisa-Sensei even if she is unwilling.’

“…Uh.” (Harold)

“Even if she survived, her ‘soul container’ maybe can’t be saved, so her future life will be bleak. She can abandon her faith, but that’s not going to be the case.” (Yuri)

‘If you are a religious person like Eisa-Sensei, it seems not possible to save your heart.’

“Damn, why did I involve Sensei?” (Harold)

He seemed to regret something.

“Well, you just have to fulfill the contract without breaking it. If you’re worried, you can roll your bottom now.” (Yuri)

“Do you think I can do that? It’s Eisa-Sensei.” (Harold)

“The vow that we made there would have to do with the navigation in the first place. Basically, if you think of a vow as a contract, it will only take effect from the time I teach navigation. If I don’t teach you how to navigate, the context of the vow itself become meaningless, but it doesn’t mean that there was no oath. If you were a defiant person, rather than going to see Eisa-Sensei, I wouldn’t tell you about the tool because I feel anxious. That was what I’m going to say. Yeah, so there’s no problem.” (Yuri)

‘If I do it that way, Eisa-Sensei will surely be convinced. So, there’s no problem. Maybe, my reputation from Eisa-Sensei will go down, but that’s not important.’

“Aah, is that so?” (Harold)

“Would you like to stop?” (Harold)

‘I also don’t want to teach anyone who is going to be defiant.’

“No… I’m a man who will do whatever I say.” (Harold)

‘It seems he will do it.’

“I’m relieved to hear it. Well then, let’s go.” (Yuri)

I climbed the stairs at the headquarters and went upstairs.

When I opened the door, there was a round table inside. This was the room I used as a conference room. The quality was poor, but the blackboard was also installed.

At the round table, my cousin was sleeping while sitting on a chair. It was Syamu. Next to her, there was a busty glasses girl sitting. It was Lily-san who finally satisfied with the completed spectacles. Lily-san was awake unlike my cousin.

“Sorry to bother you~.” (Lily)

She said it comfortably.

“Thank you. Sorry for asking when you’re busy.” (Yuri)

I bowed down my head. It was me who called her.

“Yeah, yeah.” (Lily)

“These guys are sailors. This is Harold and this is Gora.” (Yuri)

I briefly introduced them.

“Aah yes… I’d be happy if I could understand what you taught.” (Harold)

“Harold may be not able to do it, but it would be nice if one of them could understand it.” (Yuri)

“I don’t think I will die if I don’t understand, so I’m going to understand it even if I don’t like it.” (Harold)

‘It seems so.’

“Uhm, who are these ladies?” (Harold)

Harold asked.

“They are the ones who made the tool for celestial navigation. The one who is sleeping over there is my cousin, Syamu, and the other is the company’s technology chief, Lily-san.” (Yuri)

“Please to meet you.” (Gora)

Gora bowed his head.

“When I look at you both, Harold is the skipper while Gora is the navigator, is it?” (Lily)

“…” (Harold)

When I was silent…

“Yes. I’m the navigator.” (Gora)

Gora made the proclamation.

“Hmm.” (Lily)

Lily was staring at Gora.

“U-uhmm…?” (Gora)

“No, to think that it’s such a young child where I have to entrust the masterpiece that I’ve been handling with care like my child is…” (Lily)

Lily said anxiously. In front of Lily, there were two boxes. There was a large clock called a chronometer.

‘A chronometer is a clock that has been designed to function as a precision watch. It has been devised to eliminate the effect of posture changes caused by waves and it also eliminates impact. To put it simply, it’s a clock that is extremely accurate, even if it’s on a ship that always swings extremely.’

marine chronometer

Marine Chronometer

‘It’s easy to say, but to make such a watch, it needs various ideas and new inventions, and Lily-san has obtained several patents for the development.’

‘Originally, mechanical clocks in this country are made on the premise that the pendulum clock and the sundial are always matched. The accuracy is of course better, but this is more about portability.’

‘Of course, that’s not the case with chronometer. On the contrary, accuracy is more important than portability.’

‘In conjunction with Sibyaku standard time, you can sail for more than a month without adjusting the clock anywhere, and when you return to Sibyaku, the time is perfectly synchronized. Since it is a machine that requires such performance, I won’t say that it is up to one minute error within a year, but if you don’t synchronize with your one-month clock, your twelve-hour clock will go wrong. Then, such a thing is useless.’

‘Lily-san also had to consult with her parents to develop this tool since the facilities in the dormitory weren’t enough. Therefore, Lily-san’s masterpiece is no exaggeration.’

“Are you worried?” (Gora)

Gora said so.

“On the contrary, aren’t you worried about handling this? You know, a clock is a fragile machine. Yuri-kun spent one hundred gold coins to make this one.” (Lily)

“One hundred…” (Gora)

Gora was stunned.

‘One hundred gold coins aren’t the amount of money that can be obtained by a sailor. Even with this, I was offered at Lily’s ‘staff price’. If this is put up for sale with Amiens mark, it might cost two hundred gold coins.’

‘The reason why two clocks are here is they are supposed to be used in a set of two in case of breakage. The mechanical clocks can cause terrible errors or break just by neglecting the oil leveler at a single spot. If it occurs at sea, and a disaster happens, the ship will be the grave for the crews.’

‘Since that’s a problem, in order to reduce the accident rate due to human error, it’s necessary to produce two units. Since it has a mass production effect, the price is not doubled, but still, it is expensive to produce it.’

‘Apart from that, we need a watch for everyday use, so we also have one highly accurate pocket watch. Since the chronometer isn’t something to carry, it should be installed in the center of gravity of the ship if possible.

‘The actual use of the observation is the pocket watch. Pocket watches are synchronized with the chronometer every day.’

‘ That includes the sextant and the voyage yearbook made by Syamu, and it cost me three hundred gold coins, I think? It’s not the amount of money to deal by ‘Hou and Associates.’

‘Cuffe had a bitter face, and the accountant’s Beaure had a blank face. If I raise money to buy a ship, all the profits have been made since the foundation of the company will be blown away. So, I’m worried about leaving it to Harold.’

“Of course, I’m not going to tell you to understand the structure inside, but it’s troubling if you don’t remember it seriously.” (Lily)

“Yes. I’ll take it seriously.” (Harold)

“Alright, let’s start with the concept.” (Lily)

The explanation began. And Syamu was still sleeping.



“…That’s it. In principle, it’s a simple thing, right?” (Lily)

Lily-san’s lecturer was over. She stood up and had a tree made of balls. This represented the earth.

“…Ah, ugh… no, no…” (Harold)

Harold stopped speaking.

“What? If you have any questions, it’s fine.” (Lily)

“No, I couldn’t understand while I was thinking about it.” (Harold)

‘This guy is no good.’

“How about you, Gora?” (Yuri)

I said it to Gora.

“…I may need to sort out the information a bit, but I got the general idea.” (Gora)

‘I see. It may have been a good start, but that’s more than enough.’

‘In the first place, they should hear the theory of ground motion for the first time. When the knowledge hammered into the head, you may feel weird at first.’

“In other words, there is always only one place on earth where the sun goes south at the same time and rises up to the same angle.” (Yuri)

I summed it up briefly.

‘If this is also used in the lunar calendar, it will be troublesome again, but the Shanti use the solar calendar which helps.’

“Since you’re not a scholar, you just need to understand that much. It’s enough if it can be used as a tool. However, if you don’t have the knowledge, you’ll have a hard time using it.” (Lily)

“Yes.” (Harold)

‘He’s obedient.’

“Let me add to Lily-san’s explanation. Do you have any doubts about compass?” (Yuri)

“Compass, is it?” (Harold)

“Strictly speaking, compass doesn’t necessarily point north. Have you ever wondered why the compass faces north?”

“So?” (Harold)

‘Well, yeah. When you think about it, you can’t understand.’

“There is something invisible… flow of power all over the earth, and it faces north. It’s good to think that the flow is meandering. Of course, even if it meanders, it may point occasionally to the north. For example, the flow doesn’t different much between one end to another end of the royal capital. But, if you are far from Sibyaku and Karakumo, it will change a bit.” (Yuri)

“…I don’t really understand. What do you mean by that?” (Harold)

“Sure, it’s irrelevant if you sail with intuition like before. For example, if you move from this place to this place.” (Yuri)

I pointed two separated points on the desk separately with my fingers.

“From here to here, let’s say you have twice as much distance from the Suomi harbor that you always use to the Island of Aisa. Since both harbors have been visited and observed once, both latitude and longitude are known. Assuming everything is the ocean along the way, of course, you want to go straight.” (Yuri)

I moved one finger in a straight line and stuck it to the other. It was the shortest distance.

“However, if you rely only on the compass needle, the direction of the needle is slightly shifted and changing, so it’s going to move like this.” (Yuri)

I moved one finger straight while changing the angle slightly and approached the other finger. The two fingers didn’t overlap and passed each other in the distance.

“This is how you can’t get to your destination. Therefore, it’s necessary to observe it every day while the sun is out in the actual voyage and correct the position every day. Well, with the sun-only method, there is only one chance to observe it in a day, so it’s ideal to do this.

This time, I put two fingers together and moved it in a zigzag manner.

“Well, in the actual voyage, even if you don’t have to worry about this, you will need to observe every day you will repeatedly hit the headwind.” (Yuri)

‘In order to move forward with a sailing ship against the headwind, you must move in a zigzag manner while obliquely receiving the wind. This is called tacking. Of course, they are away of it because it is a basic term in the basics. After tacking, you can’t tell in which direction and how much you have moved.’

wind tacking 3

Ship Tacking

“In any case, think about compass as a guide. Then, rely on the observations.” (Yuri)

“Yes. I understand.” (Harold)

“The flow of force that moves the compass needle doesn’t change over time. If you write down the error of the compass on the map, you will see how much the error is specific to the area. Then, subtract the error from the direction of the compass, and you’ll know the exact location.” (Yuri)

“But, if the compass is unreliable, what should I consider for the direction?” (Harold)

‘On what basis? Isn’t that common sense for sailors?’

“It’s the same now and in the past. It’s the North Star.” (Yuri)

“Aah, I see.” (Harold)

‘He seems to have known about the North Star.’

“The North Star is always in the north. Now, you can see why the North Star is always north based on Lily-san’s explanation. It’s just north, so it doesn’t move, and there’s no more definite standard.” (Yuri)

north star

North Star

“Understood.” (Harold)

“Now that Yuri-Sensei’s lecture is over, why don’t you practice it?” (Lily)

Lily said so.



The practice of sitting in a fixed chair in the room, likening a rope on the wall of the room to the horizon, and the sun with a circle of paper on the ceiling, continued until the sun set.



  • This is fun chapter to learn about navigation.
  • Please watch this video about compass and why it doesn’t always point north. Thanks to the video uploader.

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