Theres also the term 'disaffected' that was coined for a psychoanalytical approach to alexithymia. Where with the studies on alexithymia, causes are often looked for in brain chemistry and the inablity to process emotions from a biochemical point of view, the term disaffectation indicates that the condition could result from an experienced overload of emotion not congruent with your integrity or identity, so feeling as a whole is eliminated to resolve that conflict, as I understood it.

It would be so interesting to know more about what made Pei Shou Yi the way he is, his history, if he grew up with it, if he has suffered trauma, neglect, if he ever had theraphy or treatment, if he studied psychological topics as a mechanism to cope, and how that career path as a doctor, whatever his exact qualifications are, helped or maybe blocked him from healing, by not allowing himself to be more than a diagnosis that seemed to fit.

In any case, the affective disorder mentioned, it might be a chronic form of depression, where apathy or anhedonia can play a role, like dysthymia, with the added self?-diagnosis of alexithymia. How much of it is 'real' and how much of it might be a protective mechanism is hard to tell, especially since Pei Shoui Yi has armed himself with the knowledge and terminology of psychology, even if it is not clear how much of an authority in those fields he, or the show's writers for that matter, really are. At times, I think his claim to feel nothing  is something he exaggerates to push Zhen Xuan away.

Yes, sooo much to explore there.

Especially when he meets that boy full of feral feelings and challenges communicating and processing those as well.

As Yu Zhen Xuan is portrayed as having Autistic Spectrum Disorder, some of their challenges actually might overlap. Alexithymia can occur in people with ASD too, although I think Zhen Xuan might not be a candidate for that. He did struggle not as much with identifying, but maybe with communicating/expressing his feelings, all that pain he didn't know where to turn to, that Pei Shou Yi of all was the first to address. The irony and sense that makes, right?

To an extent I feel like Pei Shou Yi saw and needed Yu Zhen Xuan as a mirror that completes the parts he can't see in himself, but is similar enough to allow a second look, a sense of solidarity and sameness.

A lot of imagery in the show supports that, the two same cups for example.

I also just read an interesting article, that suggests people on the autism spectrum might struggle with the cognitive part of empathy more, like reading faces and body language and deducting feelings from there, and the affective empathy part might actually be more pronouncedly felt by some, a direct instinctual picking up and feeling along others' emotions, which might be overwhelming in its intensity.

Zhen Xuan seems to brim with raw feelings and empathy when he's with Shou Yi, so they might actually complement each other there, Zhen Xuan might pick up on something from Shou Yi, that Shou Yi himself can't really name and process or completely connect to, and Shou Yi might learn to use the mirror that Zhen Xuan can provide like this, to get more in touch with himself.

It's what Zhen Xun keeps doing for Pei Shou Yi now, that they are not any longer in a dependent student/tutor relationship, with a hierarchial imbalance, that Shou Yi rightfully ended when it threatened to become more than what was needed by Zhen Xuan back then to benefit his growth.

Now that Zhen Xuan has found his footing, has climbed up those steps to an eye level equality in partnership with Shou Yi, more than he could when he was just too young, now may be the time where they can turn their focus on Shou Yi's healing as well.

And I think that after they met again, that is what Zhen Xuan does for Shou Yi, and what gets through to him after all. It's the challenging of that rigid shield of a self-diagnosis he may exaggerate to get his way, the challenging of a way of life that Pei Shou Yi has accepted for himself mostly, but through Zhen Xuan's influence, we do see cracks in that self image.

And I think he does feel things, and it is hinted at in their special ep, and through the profile-musings shown in their episode 7, that he can’t hide his feelings any longer, and that he has to stop lying to himself.

He does feel something, when he’s with Zhen Xuan, not only annoyance,  does feel something in that moment when Zhen Xuan kissed him, he just doesn’t feel he deserves to respond to Zhen Xun based on that, because Zhen Xuan deserves better in his eyes, and him pushing Zhen Xuan away is always out of the ulterior motive to protect Zhen Xuan fom him, so everything he told Zhen Xuan about his not being able to feel anything... like Zhen Xuan calles him out on it right at the beginning for lying - i don’t think we can take it all at face value, or an absolute diagosis.

The actors, and their spotify podcast have hinted at similar things, so in conclusion, I believe - and the show made that the conclusion of his arc, too, albeit sometimes very subtly - Pei Shou Yi does feel for Yu Zhen Xuan, has for a long time, it is a deep care and interest in his well being, so much that he takes himself out of the eqaution when he thinks his involvement is not beneficial to Zhen Xuan, or what he deserves, with the limitations of Shou Yi’s condition.