Subterranean exploration using ultrasonic technology.

The multi-legged heavy walker prototype, WP2, designed specifically for underground cavity exploration, is gradually expanding its surveyed range.

WP2 maintains the same base design as its predecessor but has swapped its equipment for specialized survey tools and armaments. It is linked to the offshore Alpha-Class Destroyer No. 1, which continuously analyzes the underground data it collects.

Its armament includes a single multi-barrel machine gun, a grenade launcher, and a self-defense mace mounted on one of its two manipulator arms. This mace is made of carbon nanotube artificial muscles combined with a titanium alloy skeleton, enhancing its striking power and shock resistance. The previous steel-based skeleton would have fractured under the stress of close combat, necessitating this custom-built replacement.

“After all, it wouldn’t hurt to have some close combat capability!”

Thus came the Commander’s definitive decision, leading to the installation of these weapons—a choice that no doubt added to Ringo’s workload. Incidentally, a directive to develop a pile bunker weapon is also currently in progress.

“We’re detecting numerous cavities. Within a 1 km radius, at least, there are clear signs of underground hollows. Team 3, which has advanced 2 km in a straight line, reports fewer detections but still uncovered cavities at their location.”

“Hm... But there’s nothing near Telek Harbor or Iron Town, right?”

“Yes, Commander. While Iron Town was surveyed from the air and may have overlooked smaller formations, Telek Harbor was thoroughly examined by WP2 at night. The data is precise.”

In other words, the varying sizes of underground cavities located at the fortress construction site seem unique to this area. The survey range is still expanding, but the reduced frequency of detections in Team 3's findings suggests that the activity range of the suspected Ground Worms is limited.

“However, we still haven’t found any actual worms.”

“That’s troubling in its own way…”

Even after surveying an area of about 1 square kilometer, no signs of the worms themselves have been detected. While it would be a relief if these worms had gone extinct in this region, their ecology remains unknown, which poses a problem. These creatures can bore through volcanic rock, and should they do the same to the fortress’s underground structures, it would be catastrophic.

“If we can’t establish effective countermeasures, we can’t proceed with large-scale constructions.”

“Exactly. Even if we bury barriers to block their intrusion, we can’t determine the right materials or structures without testing.”

Burying steel plates would be pointless if the worms can simply bore through them. The same applies to concrete. We need to confirm the exact mechanism by which these creatures tunnel underground.

“The complete lack of information from locals is also a problem.”

Despite ongoing efforts to gather intelligence, no useful insights have emerged. Few people travel regularly, and those who encounter the worms, such as merchant caravans, are often wiped out, leaving no survivors to relay information.

It’s unclear whether victims were attacked by worms, bandits, or accidents. Sometimes, it’s only weeks after their scheduled arrival that their disappearance is even noticed. Journeys by foot or horse-drawn carriage often deviate by one or two weeks, making such delays commonplace.

“Hmm… From what little we know, worms seem to avoid areas with dense greenery.”

Empirical evidence suggests that worms rarely appear in forested regions. Most towns are built near springs or forests, so the surrounding areas naturally remain worm-free. Similarly, roads are typically constructed to connect water sources, keeping them outside the worms’ habitat.

“Commander, regarding the Afrazia United Kingdom: It’s possible that the lakes, springs, and forests scattered across the landscape were formed by worms.”

“Oh?”

“Our ongoing surveys reveal striking contrasts in the geology of areas like the forests around Iron Town. While natural features such as land characteristics and groundwater flow are plausible explanations, it’s also possible that rock formations, riddled with worm-created tunnels, have eroded over time.”

This emerging theory suggests that worms bore holes through volcanic rock, leading to collapses in thinner sections due to wind and rain. Rainwater then accumulates, forming lakes and springs. Over time, vegetation grows in these moist, sandy areas, eventually creating soil.

This hypothesis remains unproven, but the consistent sightings of worms indicate that they are not anomalies but rather an integral part of the ecosystem. The current findings at the fortress construction site further support this.

“This area has been heavily disturbed, with parts already eroding and collapsing into sandy formations. Vegetation, moss, and insects have begun to thrive in these regions, signaling the development of a budding ecosystem.”

“I see. I thought this volcanic wasteland was barren, but it seems life finds a way to expand.”

Such phenomena could be described as the mystery of life itself. However, despite these insights, the crucial details of the worms’ ecology remain unknown.

“If we could somehow lure one to the surface, capturing or defeating it might be possible.”

“Do they even still live in this area?”

“Unclear.”

For now, surveys will need to continue. Resource surveys are being conducted simultaneously, and while the mineral yield varies, significant deposits of iron and other valuable elements have been found. Most importantly, limestone has been discovered—though it will require deep excavation, its presence raises the possibility of locally sourcing concrete.

“Continue with geological surveys and subterranean exploration. Let’s also experiment with ways to lure the worms to the surface.”

“Understood. I’ll take care of it.”

Meanwhile…

It stirred, slowly waking from vibrations transmitted through the earth.

Something was intruding into its territory.

After a long period without feeding, its body felt heavy, but if it waited in its usual spot, it would eventually catch its meal.

It was not purely instinct-driven but capable of recognizing its surroundings, assessing situations, and making decisions. This time, it planned to act just as it had before—waiting in its usual place, where prey was most likely to appear. By staying there, even with its sluggish movements, it could secure sustenance.

It began to move, its body undulating as it chewed on debris, filtering out meager nutrients while inching forward. Although it lacked a precise sense of time, it felt as though it had been a long while.

If it could feed sufficiently, perhaps it might even leave this barren territory where prey was so scarce. All it needed was to grow strong enough to endure long-distance travel. Just a little more nourishment.

The Hunt Begins

“Ringo, weak vibrations detected.”

“Understood. Continue monitoring. Analyze the timeline to determine position, depth, and direction. What’s the connection to the analysis grid?”

“Link stable. Expanding transfer bandwidth sequentially. Analysis complete—coordinates plotted.”

“Good. All systems operational. I’ll take control of WP2. Beginning communication bandwidth split. Done. Link stable. Ichigo, confirm.”

“Confirmed. Control rights transferred.”

“Control rights secured. Moving silently to target’s estimated location.”

“Vector calculation functions defined. Parameter adjustments complete. Overlaying predicted path.”

“Confirmed. Target being tracked. Estimated arrival above target in 165 seconds.”

“Target velocity stable—average speed 3.5 km/h. Projected destination identified. Designating target as P1.”

“P1 confirmed. Location identified: Sinkhole No. 43.”

“This site previously showed traces of habitation by mammals. Could this be hunting behavior?”

“Unknown. Continued observation required. Deploy seismometers in the surrounding area for precise monitoring.”