The Second Fortress (name undecided) is currently undergoing foundational construction.

To support its major above-ground structure, pillar-like components are being embedded deep underground. These pillars reach a depth of 50 meters. Since the surface is covered by relatively brittle volcanic rock, it was necessary to construct supports down to the bedrock layer, located 40 to 50 meters below ground. Excavation is currently underway, with high-strength concrete being poured into the prepared spaces.

The unexpectedly deep foundations required more resources than anticipated, and the cement stored in <The Tree> may only suffice to complete the initial construction phase. However, geological surveys have revealed limestone deposits in the surrounding area. This discovery has paved the way for locally sourcing the cement needed for construction. Alongside the foundational work, excavation facilities are being built.

Incidentally, while rebar is typically used in concrete foundations, the current shortage of steel has led to the use of carbon nanotube fibers instead. Although the cost difference between steel and carbon nanotubes is astronomical, the lack of steel left no alternative. On the bright side, the reinforcement provided by carbon nanotubes has reduced the overall volume of concrete required, which is a small consolation.

"Developing specialized equipment to use carbon nanotubes as aggregates was necessary, but it won't go to waste, as we can continue using it in the future," Ringo remarked.

Ringo explained that while rebar-based foundations could have been handled with existing universal manufacturing equipment, carbon nanotubes required entirely new concrete foundation-laying machinery. This specialized equipment is currently at work, building foundational pillars at the base of the excavated vertical shafts by ingesting supplied materials and steadily erecting the supports.

For the record, the addition of short carbon nanotube fibers to the concrete mixture has turned the material significantly darker—a trivial observation.

Resource Discovery and Mining

While foundational work proceeds, boreholes are being drilled for geological surveys in the surrounding area. Although limestone distribution has been confirmed, further excavation is being conducted to identify other resources.

This has led to the discovery of a large volcanic ore deposit a few kilometers inland. While its iron content is relatively low, the deposit contains potentially extractable resources such as nickel, copper, chromium, and platinum. It appears that a lava pool formed in a depression, with metallic resources settling at the bottom.

Additionally, the surrounding volcanic rock contains traces of iron oxide, suggesting a nearby iron ore deposit. Iron, being relatively light compared to other metals, likely precipitated in the upper layers and was displaced to another location due to tectonic pressure. Surveys are ongoing around the discovered ore deposit.

Plans are also being considered to introduce an element-accumulation system, which would process large volumes of volcanic rock to remove silica (silicon dioxide) and collect other elements. Such a facility would need to be substantial due to the processing scale, but it could extract aluminum, calcium, iron, magnesium, titanium, and other valuable elements. While the process generates large quantities of silica, solidifying it and returning it to its original location should resolve waste disposal issues.

The primary challenge is the energy demand for processing. Installing additional fusion reactors would be necessary.

"I’d love to introduce this element-accumulation system, but building the required large facility and energy reactors would consume an enormous amount of construction materials…ugh, it looks like the required resources exceed those of the Second Fortress," Eve noted.

"Yes, Commander Ma’am. Even with minimum processing capacity, the facility would need to be at least five times this size. That’s equivalent to seven Second Fortresses," Ringo confirmed.

"…That’s insane."

Upon review, the idea was deemed premature. Instead, resources were prioritized for constructing seabed platforms. At the very least, iron oxide ore deposits have already been discovered on the ocean floor, though at depths exceeding 1,000 meters.

Excavation and Refinement

To extract the discovered ore veins, large excavation machinery is under construction. Since the deposits are relatively shallow, plans are underway for open-pit mining. Explosives will break apart the ore, and massive rotating buckets will extract it efficiently.

Nearby refinement facilities are also being built to process the metals into ingots. These ingots will either be consumed by construction printers at the Second Fortress or transported to <The Tree> for use. Once these facilities are operational, <The Tree>'s resource management will see significant improvement.

"Commander Big Sis, when this gets up and running, there are so many things I want to make…" Olive, the youngest sister, eagerly shared.

"Oh, really? Well, how about we make a wish list of what you’d like to build?" Eve replied with a smile.

During this inspection, Olive successfully sweet-talked her older sister, Eve. As a budding creator with a passion for crafting, Olive rarely made such requests, so Eve was quick to indulge her. It was, of course, Ringo’s suggestion.

Cement Production

Cement for the Second Fortress will be sourced from the limestone deposits. Since these deposits are entirely buried underground, tunnels need to be built to access them. Small shield machines are currently digging toward the veins. Once the veins are reached, conveyor belts will be installed for continuous ore extraction.

The cement will be mixed with aggregates and modifiers before being transported to the construction site as ready-mix concrete. Given the large quantities needed, large transport vehicles equipped with mixers are being prepared. Since there were no specific advantages to making these vehicles multi-legged, they were equipped with wheels, much to Eve’s disapproval.

Ringo ignored her objections.

Observations of the Worm

"Big Sis Commander, it’s gotten a bit bigger!" Utsugi reported.

"It’s starting to poke its head out as soon as we get near, Big Sis Commander," Erika added.

The worm was being successfully domesticated. Utsugi and Erika, the third and fourth sisters, were taking turns caring for it. The creature eagerly consumed the fish provided to it and continued to grow.

According to Ringo’s observations, the worm seemed to eat nothing but fish. If it could grow on such a narrow diet, it likely had a very efficient digestive system or a simplistic biological structure. Alternatively, there might be some unknown factor at play. While it was unclear whether its survival and growth processes were separate, its ability to grow by consuming dead organisms was apparent.

Some samples of its shed tissue, believed to be from its growth process, were collected and were undergoing analysis.

"What about its genes?" Eve asked.

"We’ve detected them. Preliminary analysis shows no matching patterns with known organisms," Ringo replied.

The presence of genes indicated a biological structure consistent with known life forms. While it was evident the creature was a "monster," understanding its divergence from known organisms could pinpoint where magical elements played a role.

"It’d be ideal to capture additional specimens for dissection," Eve suggested.

"We’re looking, but they’re hard to find," Erika admitted.

"Unless we explore deeper inland, it seems unlikely," Utsugi added.

While using the Albatross airship for exploration would expedite the process, it was currently fully occupied with ore detection and mapping, leaving worm tracking a low priority.

"Can’t we deploy some electrically powered drones? With a range of a few hundred kilometers, even battery-powered ones should suffice," Eve proposed.

"Yes, Commander Ma’am. Attaching detection equipment would drain power, but a range of 100–200 km should be achievable. Until the microwave power transmission system is operational, we’ll use small drones for surveys," Ringo confirmed.

"Commander Big Sis, I want to make drones," Olive chimed in.

"Oh…"

Thus, instead of repurposing existing drones, Utsugi, Erika, and Olive began developing specialized drones for worm exploration. This marked the first collaboration between the three sisters, potentially sparking new ideas. Eve and Ringo would oversee resource allocation while allowing the sisters to freely (and chaotically) design their project.