"Above ours is a hot spring?" Tadao was surprised. "How could it be..."

Everyone else was surprised.

"How can it not be a hot spring?" Conan asked rhetorically.

"What do you mean?" Tadao was even more surprised.

"First of all, in terms of hints, this treasure is comparable to gold taels and rice and one stone, and if you use this kind of hint, then it is also a certain indication that the final treasure is neither gold nor rice, but something else. Excuse me, in the Warring States period, what might the Takeda family use as a resource for a comeback? ”

"Uhhh Everyone was a little speechless, and even Tadao obviously had a tricky feeling that there were too many possibilities to start.

"Then I'll ask a different way," Conan asked, shaking his head helplessly. "What resources does the Takeda Shingen family have that future generations can continue to use and that can be properly preserved here? Hint, start with the advantages of the Takeda family over other princes. ”

"The advantages of the Takeda Shingen period... After narrowing down the search, Tadao was finally able to make an inference. "The first-class retainers group led by the four Takeda ministers, the top Takeda cavalry corps in Japan, and the abundant gold resources, efficient hot spring recuperation resources, and outstanding horse resources possessed by Koshu itself!!..." As he spoke, Tadao himself discovered the answer.

"The retainer will die, and it is impossible to resurrect him after the resurrection of his descendants. Ditto for the Takeda Cavalry Corps. Conan continued his commentary. We vetoed the gold ore resources before, so it's not. The horse resource itself requires a large amount of land and a staggering consumption of grain and grass, and it is impossible to hide. Then, there will only be one answer left - what is it? Please answer! ”

"The hot springs of the Takeda family!" Tadao muttered.

"The treasure is ... Hot springs? Kimura had an expression of disbelief.

"As proof," Conan pointed to the plank where everyone had stood. "The plank was rotten, probably because of soaking or something. And there should have been a mechanism underneath that plank, the one I mentioned earlier, which is used to sense a weight of 150 kilograms. But the mechanism was gone, and all that was left was some damp, green paste. ”

"Is it moss?" Motota asked.

"Ferrous sulfide, FeS, ferric salts are pale green in solution." Gray Plains Wai already understood what Conan meant. "It can be produced by the corrosion of steel materials by hydrogen sulfide in hydrogen sulfide hot springs, so there would have been some metal mechanism underneath."

"Hydrogen sulfide... Tadao also understood the meaning of Gray Hara's mourning. "Hot springs... Are you saying that there used to be hot springs here? ”

"In other words," Conan nodded. "The hot springs flow out of here, fill the entire space, and then spring up to become hot springs for your use. As for the nature of this metal mechanism ... I guess it's a weighing mechanism. The heavier the plank, the deeper the metal mechanism will be pressed. When pressed to a certain depth, the mechanism is triggered, and the hot spring flows out of the mechanism. However, the designers of the mechanism did not understand chemistry, so they did not know that the metal mechanism was corroded by the erosion of hydrogen sulfide. For this reason, the mechanism used to weigh the hot springs was weakened by the inflow of hydrogen sulfide hot springs through the cracks, and eventually they could not bear the weight of 150 kilograms, and they crumbled into slag under heavy pressure, which is why the hot springs stopped flowing. ”

"However, it has been hundreds of years since the Warring States Period, right?" Mitsuhiko asked curiously. "Why did it corrode only three years ago?"

"There's not much hydrogen sulfide in the hot springs, and when the outside of the metal mechanism is corroded, it also forms a protective layer that prevents the inner layer from continuing to corrode. That's why the whole corrosion process lasts so long to complete. ”

"So, the weighing mechanism was completely damaged and the hot spring's gushing mechanism was shut down as a result?" Tadao's expression was obviously helpless. "So, is there any other way to revive this hot spring? Or is it ... No way? ”

"I don't know how corroded the whole mechanism is, and it's likely that there is no way to open the vent in the normal way... Conan spreads his hands. "But if you can pry open the bricks of the spout, maybe you can give it a try."

"Don't talk about that yet," Qianyu's expression suddenly became a little distressed. "Have you ever thought about a question?"

"How are we going to get back!?"

"Thousand feathers," Conan asked, glancing at the hole. "Was it difficult for you to come down? Did that hole have a lot of margin when you passed? ”

"It's no more than 5 centimeters, and I was scratched when I came down, and my shoulder still hurts... Qian Yu pursed his lips and replied. "If we go back from there, we'll be fine, but Brother Tadao will be in trouble."

"If Brother Tadao can't get through, then there must be some mechanism here that can open the door to get out!" Conan immediately concluded. "Otherwise it simply doesn't make sense."

"Unreasonable?" Tadao was a little strange. "Why is it unreasonable?"

"There is a hot spring above our heads, and there must be flat ground near a hot spring, so the height of the altar just now must be lower than the normal water level of the hot spring." Conan explained. "In other words, under the normal condition of the hot spring, if there is no mechanism to lock the staircase where we come down and isolate the water from the side of the altar, then the altar will definitely be submerged, and the wooden Koshu Dou will float, then it will be impossible for us to see Koshu Dou lying quietly on the plate!"

"If that road is blocked, and the hole above is impassable, then who opened this hot spring mechanism in the first place?" Conan continued to explain. "If it's the dead man who comes in and opens the mechanism, just like Chiba said before, the bones of the dead man will pollute the water source, making the hot spring unusable at all. Therefore, there must be some escape mechanism here where the person who opened the hot spring mechanism can escape. ”

"But if we can't find a trigger for that mechanism, we won't be able to get out, right?" Qian Yu asked with a frown.

"Uh... yes... Conan realized that his idea also had a loophole and said embarrassedly.

"Anyway, I have an idea." Qian Yu suddenly thought of something. "Mr. Kimura, Mr. Tanaka, back away, leaning against the stone wall unknown."

"You're not trying to trick us, are you?" Kimura asked.

"Just to be on the safe side," Qian Yu said as she aimed the crossbow arrow on the tip of the Traceless Umbrella at the two of them. "Please back off!"

Kimura and Tanaka had no choice but to retreat to the stone wall behind them—right next to the strangely colored wall brick—eight or nine meters away from the crowd, and more than five meters away from the two guns.

"Conan, bring those two guns," Chiba continued. "Everyone stay away from those two, but also away from me, just stand more than 5 meters to my left and right."

“。。。” Conan glanced at Chiba, who was still standing where he had been rappelled down before, and then walked over to the gun. "Is the stone wall between the hot spring up there and our space thin?"

"Thin! It's very thin! Qianyu looked at Conan and nodded with a smile. It's up to you! ”