There's a deep-rooted kindness and tenderness within An Zhe and Lu Feng that both of them seem to recognize within each other over the course of the novel. An Zhe as a Mushroom consuming some of An Ze's DNA ends up helping An Zhe meet his goals, but initially he sees the distressed human in pain and he wants to help. Never mind that he's just a mushroom and can't do anything to help him survive, he tries his best to take away the pain and staunch the blood flow. Ultimately it is useless, but he gave An Ze relief at the end of his life with companionship and kindness.
Lu Feng, as Arbiter with the license to kill without needing to report to anyone his reasoning, is introduced as a tyrant and villain. Even An Zhe's first impression upon meeting him is fear and unease. However, Lu Feng defies our expectations. Instead of acting upon his first instinct, the moment he feels doubt, he pulls back and turns to someone else for a second opinion to be absolutely certain. That is not the act of a cold and callous person. Lu Feng cares deeply for the people within the city. He would prefer that they all have a happy life and do not meet their end by his hand, but he also has to recognize that if he lets someone go who is infected, he could end the human race entirely.
Lu Feng does not allow himself to doubt his judgement to protect the people within the city, and unfortunately he meets a lot of resistance because of the role he plays in that. An Zhe can recognize how isolating it must be to be Lu Feng. Although he is afraid of him, he also feels sad for him to have to stand there and see people protesting him doing his job to prevent them from experiencing the kind of horrors Lu Feng has seen during his time as Arbiter. It is a job no one should ever have to do. Looking human beings in the eyes and determining whether they're a danger to their community and should be put down is a heavy job to give to anyone, so much so that being an Arbiter is historically a short-lived position.
Its a necessary evil, and an excruciating one. Its a responsibility that Lu Feng bares in the hopes of keeping as many people alive as possible while sparing everyone else of having to share the burden. Its the kind of job that can have a lasting impact one's mental well-being that can not be understated.
An Zhe, in choosing to stay with Lu Feng when the protestors are shouting for his head, offers to shoulder some of that burden with him. He does this despite being a xenogenic, despite his fear of Lu Feng finding out and killing him, despite how people warn him away over and over again by condemning Lu Feng for "senseless killing". An Zhe's empathy is unmatched. Although he does feel as though all of these awful things have nothing to do with them, he listens, he watches, and he cares for the people he meets and hopes for their good health and fortune.
An Zhe and Lu Feng are evenly matched in their humanity. An Zhe may have started as a delicate little mushroom, but his drive to survive, desire to care, and empathetic nature makes him just as human as the rest of the people Lu Feng strives to protect.
