Tetsu no Sosuke muttered to himself, "It must respond to faint light... A particular kind of light triggered the mechanism and opened the entrance. Any other light—brighter or dimmer, from a different angle, or at the wrong time—probably wouldn't have worked. The depth of the Mechanism Arts really is astonishing."
In truth, this world itself was a vast miracle.
Against that, none of the miracles humanity had created seemed particularly remarkable.
Shinobu Kocho heard him, but she had no idea what he meant, so she didn't ask.
Tetsu no Sosuke, on the other hand, was delighted with himself. "The first night that Demon appeared, I opened my eyes and saw the stars. That was when I realized what the map showed... The marks on it weren't swamps at all. They were the sky. The circles of different sizes were clusters of stars. Yuichiro and I had been focused on the ground, never thinking the real answer was overhead. But with Demon showing up too, I couldn't come looking for this place right then..."
"Oh." Shinobu Kocho nodded and decided to pretend she understood.
Tetsu no Sosuke didn't care whether her answer was perfunctory. He was too pleased to have found the place.
He was still enjoying his triumph when a sudden series of clicks came from the tunnel entrance behind them. Shinobu Kocho reacted at once and sprinted back. Tetsu no Sosuke hurried after her, but by the time they reached it, the entrance above had sealed shut.
Tetsu no Sosuke's face darkened. Shinobu Kocho went pale.
They stared at each other. At last, Shinobu Kocho said, "Don't you know the Mechanism Arts? Try opening it."
Tetsu no Sosuke searched all around before shaking his head. "I can't. A mechanism has to leave some trace, some way to work it.