I decided to transplant some of the Dungeon Potatoes that were being grown inside the Sun Castle to the fields outside. I would have felt terrible if I’d moved them all at once only for the entire crop to fail, and I also had lingering doubts about whether potatoes grown indoors could survive the transition to the open air.
I wondered if it might be better to create an underground cellar or tunnel for them. Apparently, the ground of the Sun Castle was at least three hundred meters thick, even at its thinnest points, so digging a little wouldn't result in punching a hole through the bottom. However, since the castle’s basement levels extended through the center of the structure, the residents asked me to refrain from digging too deep.
Well, if an underground tunnel was out of the question, I suppose I could just build a roof over them. For the time being, I would just have to wait and see how the transplanted potatoes fared.
Next, there was the matter of the Sun Castle’s flight. It utilized a magical power source fueled by refined Heat Retention Stones. According to Lu and Tia, this was a remnant from an era when magic technology was far more advanced than it is today. Even as a mere relic, it was overwhelmingly superior to modern magical techniques. If we could analyze or replicate it, it would surely be useful in various ways.
"Just because someone can ride a horse doesn't mean you should expect them to know how to breed them," Bell replied when I questioned her about it.
In other words, the pilot and the engineer were two different roles, or perhaps the operator and the manufacturer were distinct. Even among car drivers, not every person knows how to perform maintenance on their vehicle. Expecting someone to build an engine from scratch was simply asking too much.
Even so, Lu interviewed her about the parts she did understand and recorded everything on paper. Unfortunately, it wasn't proving to be very helpful. The issue was that the vast majority of Bell's knowledge was based on the technology already being in a completed state. To use an analogy, it was like being taught about operating systems and applications before the concepts of smartphones or PCs even existed. Furthermore, Bell didn't have the necessary knowledge to explain those underlying concepts. All she could do was explain how to operate the software.
According to Lu's estimation, if we gathered the top experts in current magicology and had them immerse themselves in research for about a hundred and fifty years, they might manage to figure something out. By the way, Lu and Flora—who would both be among those top experts—already said they would pass on the project. Lu explained that she didn't have the heart for research where the goal was already set in stone. Unless one was driven purely by a bottomless pit of intellectual curiosity, she found such work tedious. She also mentioned it would be a long time before such research turned into a profit.
As for Flora, she was simply too busy with her research on fermented foods.
Speaking of which, I was surprised to find that the natto fermented much faster than I expected. In my mind, I thought it would take about ten days, but the bacteria had completely colonized the beans within a single day. Because of that, the first batch was a failure due to over-fermentation. For the second attempt, I checked on it every few hours and found that roughly one full day was sufficient. After that, it took several more failures before I realized I needed to let it mature at a low temperature to suppress further fermentation.
While we hadn't started mass production yet, the reputation of the prototype was quite good. However, due to the unique smell, there were some people who just couldn't handle it. I wasn't particularly fond of it myself, either. Just like with the Dungeon Potatoes, I intended to look for a way to make it more palatable.
Returning to the topic at hand, learning the Sun Castle's magic technology through verbal instruction seemed impossible. I thought about looking for documents instead, but they had succumbed to the castle's long, troubled history. In short, there were no manuals left. All that remained were various texts scattered throughout the study and other locations in the castle. Some of these dated back to when the Sun Castle was first built, while others were left behind by visitors. As a result, the collection was a disorganized mess of subjects. There were works related to magic technology, but just like Bell's knowledge, they weren't very practical.
It was a shame, but since they were apparently valuable as reference materials, they let me take them along with several other books. I set up bookshelves in the hall of my mansion to house them. Some of the residents seemed to enjoy reading them, though I wondered if they actually understood the content. Since I saw them laughing, there were likely a few storybooks in the mix. I decided I’d try reading some myself next time.
Currently, the Sun Castle, having been replenished with a massive supply of Heat Retention Stones, was set on a course that would take it one year to circle the perimeter of the Forest of Death. It moved in a counter-clockwise direction. This course was primarily Gou's idea. The Sun Castle wasn't built for speed, but he wanted it to keep moving rather than remain stationary. Since Gou's role was tied to navigation, he felt he had no purpose if the castle didn't move. I thought his role as the caretaker for Kuzuden and the others would be enough, but apparently, it was a matter of identity for him.
So, we decided it would move. However, since it now belonged to the Village of the Great Tree, I worried it might cause trouble if it left the Forest of Death. Lu and the others told me not to worry about it, but I felt it would be a problem if the castle wasn't in a place where we could contact it immediately. Therefore, we agreed that the Sun Castle would only travel through the airspace above the Forest of Death.
With that settled, a course circling the outer edge of the forest was proposed and approved. From the perspective of the Village of the Great Tree, the Sun Castle would be in the northern sky in winter, the western sky in spring, the southern sky in summer, and the eastern sky in autumn.
Was it basically a massive calendar? Once we got used to it, we might be able to track the seasons simply by looking at the castle's position.
Even though the Sun Castle was moving, getting there was a bit of a hassle since you had to be carried by someone who could fly. We began considering other methods of transportation. Before that, I checked one possibility: was there anything like a teleportation device?
Apparently not. Back when the Sun Castle was built, teleportation magic was considered Forbidden Magic. Users were immediately arrested, and even learning it was illegal. I wondered why, but it was simply for the sake of crime prevention. It’s true that someone could do whatever they wanted if they could teleport anywhere. It was a type of magic that required immense self-restraint from the user.
I thought of Beezel and Progenitor-san. Well, they were probably fine. Nowadays, teleportation magic wasn't a crime, but it was considered good manners not to travel directly into a house, or even into a village or town.
As for other transportation methods, I suggested balloons or airships based on my own knowledge. I didn't have enough technical knowledge to suggest airplanes. Others suggested having people learn flight magic or teleportation. That sounded like a very long-term project.
The Mountain Elves really bit onto my suggestions, so I wanted to try making them, but whether it was a balloon or an airship, we would need large, sturdy cloth. Apparently, it could be reinforced with magic, but it would probably be better to wait for Zabuton to wake up for that. The Mountain Elves were eager to start on the hull of an airship immediately, but I stopped them.
Technology advances step by step. I had learned that much from the Sun Castle. First, we would try a balloon. And not one large enough for people to ride, but a small one for experimentation. I told them not to look so disappointed; the basket aside, the device to stably send heat into the balloon was going to be quite a challenge.
"You're right. We'll do our best," they replied, and I was satisfied with the answer. For the time being, we would continue to rely on those who could fly to carry us.
When I looked at the big picture, it seemed like the technology provided by the Sun Castle wasn't actually that spectacular. But there was one incredible piece of technology I found. Its weakness was that it couldn't be produced elsewhere because the machinery was fixed to the Sun Castle, and the production volume was low, but I still thought it was amazing.
Canned food.
Yes, the Sun Castle was capable of making canned goods. After producing Dungeon Potatoes, the Devil Race and Dream Demon Race had been turning them into cans for preservation. Of course, they needed iron to make the cans, but the fact that they could manufacture thin iron cans was impressive. The fact that they could seal them airtight was also incredible. As for how to open them, you needed a can opener. It was a shame they weren't the easy-open pull-tab type.
Still, it was canned food. It made long-term food preservation a reality. It was truly a pity the production volume was so low—only ten cans a day. However, that was a hundred in ten days, and a thousand in a hundred days. On a yearly basis, that was over three thousand cans.
Yeah, that should be enough. I was sure Michael-san would be pleased. There was a possibility the numbers would increase once more of Gou and Bell’s comrades woke up, so I looked forward to seeing how things developed.