They followed Zero's detected trail forward, encountering four extremely well-hidden mines along the way, each placed where footprints had passed.
At the same time, the closer they got to the center, the more miscellaneous traps appeared.
There were pressure-triggered potato mines, sensor mines hanging overhead, and even primitive arrays of spikes activated by stepping on a board.
Zero continuously reported the detection results while also providing the other party's approximate location.
It was a round manhole cover about eighty centimeters in diameter.
All the footprints converged there before vanishing. It seemed they had gone down through it.
"Into the sewers?"
These natives were far more skilled at defense than the people from the Five Building District.
Even Zero's detection ability was restricted, repeatedly warning that its signals were suffering severe interference.
Of course, it was also possible that the blue-purple slime was growing more luxuriantly underground, crowding out the living space of countless other organisms. Once dispersed, even if some signals could be sent out, they would be absorbed on the way back and be unable to return any useful information.
Time slowly passed as wave after wave of signals scattered outward.
After roughly four or five minutes, Zero's energy began sounding an alarm again. The 2.98% charge accumulated during the day plummeted once more to 0.1%.
Only then did his voice come through, barely projecting a calculated image before them.
"Master, after comprehensively calculating all the returned data, I have derived an approximate model of the structure beneath the manhole cover."
"Because a large amount of slime is attached to the building walls, I cannot continue probing farther inside unless you can descend below."
In the image,
the shaft beneath the manhole cover extended vertically downward for about fifteen meters before becoming a steep slope.
The slope continued downward