As for why Youji was so excited, Xiang Shan knew perfectly well.
The boy was so happy because Xiang Shan had agreed to teach him some skills.
Xiang Shan admitted that revealing his identity had been somewhat risky. He had even considered the worst-case scenario—that the words "knight-errantry" had been completely twisted in this era, and Vagrants no longer had any reputation to speak of. In that case, he might have had to knock Youji unconscious and leave the town.
But he truly lacked common sense about this bizarre era. He needed someone from this time to help him. Besides, some modifications involving the brain could not be completed alone. If he wanted to recover his martial arts, he needed an assistant.
Youji was currently the only person Xiang Shan could trust. He had spent several months with the boy and knew that he was kind by nature and quite clever. He was also curious enough to want to understand this world.
In Xiang Shan's eyes, the boy was worth training as an assistant, perhaps even a disciple.
Xiang Shan had also given some thought to revealing his identity.
After weighing the risks against the benefits, Xiang Shan had ultimately chosen to be honest.
A few minutes earlier, Xiang Shan had watched Youji's expression shift from shock, to fear, and finally to relief.
"I saw how angry you were over what happened to the workers," Youji had said. "I believe you're a good person, a good Vagrant."
After that, Xiang Shan asked Youji where he could buy parts and borrow a set of specialized tools. Youji brought Xiang Shan to Doctor Schultz.
"Mm, most of the parts you need are quite common. I have most of them here." Doctor Schultz glanced over Xiang Shan's list and nodded. "But a few of them aren't cheap, so..."
"Don't worry, I have a way to pay." Xiang Shan took a spinal bone from the pack he carried with him. It gleamed silver-gray and felt heavy, unlike a buildup of calcium and protein. Its density was close to that of metal.
This was a relic left behind by Will Grand Dog: a vertebra.
Humans really could grow spinal bones like this. Xiang Shan had just remembered that. In the twenty-first century, humanity had made enormous advances in molecular biology and genetic engineering. Through genetic modification, humans could make their bodies synthesize proteins containing metallic elements.
If someone used modified viruses to splice entirely new gene fragments into their body, then continued taking immunosuppressants for a time to suppress the rejection response between their original body and the newly formed proteins, the cells made from those proteins would gradually replace the original cells, eventually allowing the person to evolve from Homo sapiens into an entirely new organism.
And this new species of human, transformed from Homo sapiens, possessed far greater adaptability toward cybernetic prosthetics. The Metal-Based Protein in their bodies formed natural wires and resistors, infinitely lowering the threshold for brain-machine interfaces while drastically increasing cellular resistance to mechanical damage. Implanted hardware would no longer cause the death of surrounding cells.
—Perhaps that was also why Xiang Shan could awaken again after being unconscious for countless years.
From a certain point onward, humanity's march toward prosthetic enhancement had galloped forward like an unbridled horse.
Xiang Shan no longer remembered the finer details. But he did remember that in his era, the spine had remained crucial. A metal-based spine was a natural data transmission line, with tremendous channel capacity and innate compatibility with neural signals, requiring no further adjustment. Many cybernetic modifications retained the brain, cerebellum, medulla oblongata, and spine as a complete set.
And now, Will Grand Dog's martial artist prosthetic still used this technology.
Xiang Shan remembered that Youji's mother, Yulia, had once sold a spine. It was evidently still very valuable.
Doctor Schultz jumped. "You're selling this?" He looked at Xiang Shan's stick-figure-like prosthetic body. "You don't plan on using it yourself?"
Xiang Shan feigned indifference. "No medicine."
"Medicine?"
"The kind... needed when replacing a spine... what was it called?" Xiang Shan asked tentatively.
After receiving metal-based gene fragments, cells became more resistant to apoptosis, and the receptors on their membranes were completely rewritten. Earth's native viruses could barely harm these new humans anymore. In addition, their elevated body temperature made humans immune to most old bacteria, fungi, and parasites. But that did not mean rejection reactions no longer existed. Using someone else's spine would still cause a rejection response.
—Of course, that was how things had been in the era Xiang Shan remembered.
Xiang Shan did not know how far Earth's technology had advanced after he fell unconscious. Youji was not familiar with such specialized questions either, so Xiang Shan could only probe Doctor Schultz.
Doctor Schultz nodded. "That's true... Anti-Messenger Immersion Agent is indeed hard to get."
He did not suspect much. After all, ordinary people would never need to replace their spines in their lifetime.
"Yes, yes, Anti-Messenger Immersion Agent!" Xiang Shan nodded, pretending to suddenly remember—fortunately, he had neither face nor skin now, and even his voice synthesizer was cheap and emotionless. He did not need acting skills.
—Anti-Messenger Immersion Agent, a term I've never heard before... Messenger molecules, does that have something to do with messenger RNA?
Xiang Shan himself had been an engineer. But he vaguely remembered a friend in biology mentioning related topics to him.
—The Central Dogma: DNA records genetic information into messenger RNA, then messenger RNA transcribes it into polypeptide chains, which are folded by organelles into proteins... Reverse transcriptase? No, probably not...
—Had this process now been further reversed?
It seemed technology had continued to advance. That was Xiang Shan's conclusion. In his era, aside from exceptional cases like prions, nearly all life processes followed the biological genetic information expression process known as the Central Dogma. It was nearly impossible to reverse such life processes inside the cells of an advanced organism.
"However..." Doctor Schultz flipped to the end of the list and looked it over. "I really don't have these parts... Specifications like these shouldn't be used in prosthetics, should they? And the last item: sheet metal less than one millimeter thick and under three centimeters wide? If you're looking for that sort of thing, you'd be better off going to the scrap-parts collection bins at the eastern end of town."
Xiang Shan explained, "They're for making some... auxiliary tools."
"Judging from this list, you haven't received professional training, have you?" Doctor Schultz shook his head. "Many of your specifications are written improperly. I don't know what kind of prosthetic you intend to make, but professional martial artist prosthetics are rare things, after all. I wouldn't want you to waste hard-won good parts. How about this? Would you like to go online and look at some design blueprints?"
"Go online?" Xiang Shan was startled. He remembered that the internet had once vanished because of war. He had never expected this dilapidated-looking world to still have something like network signals.
"Our town is rather shabby, so we don't have public network coverage. But I set up a private network at home. If you sit in the middle of the living room, you should be able to receive it. I can give you a one-time access password..."
At that point, he paused. "But you'd better not download things casually, and don't enable previews for holographic signals either..."
Xiang Shan was indeed tempted.
But in the end, he shook his head. "No, Doctor, thank you for your kindness. Network access must be expensive. I can't take advantage of you for nothing."
"That spinal bone has already earned me quite a bit." Doctor Schultz patted Xiang Shan on the shoulder. "Besides, you saved my town. I really should thank you."
"No, I'm not used to accepting favors for no reason. If I need it, I'll come borrow your network again." Xiang Shan still refused Doctor Schultz's goodwill.
Doctor Schultz did not invite him again. He quickly gathered the parts Xiang Shan needed and lent him a professional set of biological tissue surgical tools.
After confirming that Xiang Shan had gone far away, Schultz went upstairs.
The mayor was in one of the upstairs rooms.
"Uncle, he didn't go online." Schultz wore a strange expression. "Why did you tell me to make sure I invited him to?"
Doctor Schultz truly did not understand his uncle's request. Still, he had done as he was told. His uncle was the most knowledgeable person in town. When he was young, he had traveled far and wide and learned certain secrets.
"Dresden..." The mayor called Schultz by name. "Turn off the network first."
Schultz nodded and directly issued a command through his brain-machine interface, disconnecting the home network.
After all, this was how he usually saved on network fees.
"Do you know, Dresden?" The mayor seemed to be recalling the past. "When I was young, I offended an official and had no choice but to flee far from home."
Schultz nodded. "That's right, but you were lucky. That official died later..."
"He was assassinated by a Vagrant." After a moment of silence, the mayor said, "I was the one who called that Vagrant there..."
"What?" Schultz screamed.
Colluding with a Vagrant was a grave crime against the Dyson Principles!
"I did not collude with a Vagrant. I merely happened to encounter one in the wilderness and asked for help." The mayor snorted. "Your grandfather, my father, once told me that thugs like Vagrants were actually easy to use. As long as you acted humble before them, they would not make things difficult for you. On the contrary, driven by some twisted sense of honor, they would assassinate officials they believed guilty—they were actually very easy to use. This was a very important piece of survival wisdom for us."
Schultz cried out, "You never told me that..."
"That was before... The fewer people who knew this secret, the better." The mayor fell silent for a moment. "But now, things are different. The tax collector only took eighteen infants, below the required proportion. We don't know how he intends to deal with us. Perhaps we can only rely on the power of the Vagrants."
Schultz immediately understood. "You mean... Shan is a Vagrant?"
"I don't know what Mister Shan did before he lost his memories, but I know that all Vagrants share one habit: they do not connect to the network casually. I spent a few days with a Vagrant once, and before going online, they always made lengthy preparations." The mayor spoke softly. "I don't know whether Mister Shan is a Vagrant. But he certainly can fight—especially after obtaining that martial artist prosthetic."