zhou zishu's martial arts being something that at the beginning of the book makes him an instrument, strips his identity and personhood from him, keeps him away from human connection and actively destroys his previous relationships, but then becoming the reason he can gain control of his life back (his abilities let him escape tianchuang's control), he can affirm his individuality and personhood (the way he talks about martial arts as something that he gained with practice and is impossible to cut from him if he wants to keep being him, the way he is proud of his four seasons manor techniques), he can form meaningful connections again (with wen kexing, his zhiji, a connection entirely based on martial arts and sparring for slightly different reasons in the drama and in the book, and with chengling, his disciple).
this imo ties with his journey through what masculinity means. i don't think it's only that, but it's important to note that in the book, he despises physical and romantic touch, except when he's sparring with wen kexing, an activity they both use as a replacement for sex. they form an instant connection based on martial arts, they immediately become obsessed with each other, but they both work a lot on what "being into men" means, because as it stands at the beginning of the story, they're incompatible, except when sparring, where they're not only equal but also easily falling into place together.
from zhou zishu's part, he sees sex as a need to be satisfied to be in your prime, and also a degrading thing for one person in the relationship, it's something that one person does to another and it's often not that pleasant for the one receiving it. it's a strikingly similar starting point to the martial arts one. through his relationship with wen kexing, one mediated by martial arts and its changing meaning in zhou zishu's mind, he changes this point of view so radically that in the end, he is able to not only show vulnerability, but ask for it in return ("are you sincere?"). he bottoms in the extra, and he does so following wen kexing's profound display of vulnerability. he deeply trusts him and knows he can do what in his mind is the most vulnerable thing to do (bottoming) with him because wen kexing has shown him extreme vulnerability in return (being open with his feelings instead of wearing a mask). in a similar way, at the beginning of the book their sparring sessions are explicitly directed at immobilizing the other (notable scene where wen kexing blocks zhou zishu's qi to gain sexual advantage on him), while in the end they just go on and on dishing out the worst they can because they both know the other knows all their dirty tricks and has equal capabilities of retaliation.
