I recently watch a documentary about sociopaths and it was maintained by the behavioral analyst, psychologist and sociologist involved, that there ARE some with these tendencies who do fall in love. Those who love them back, who truly understand them, understand that they can't control their minds and compulsions. So, I believe there's a small part of Kang Moo that might actually love Kirin or understands (to a point) that someone loves or cares for them. It's not necessarily all one-sided love.
That’s the thing, people always assume love is just an emotion. But love is also a choice. A sociopath and psychopath might not feel empathy, but they can have fond feelings for someone, and they can CHOOSE to love someone. I think Kangmoo does love Kirin, just not in the way regular humans love each other. It’s a selfish and somewhat manipulative love, but also not because he does so much for Kirin at the same time? and it’s not entirely based off a feeling like how we describe love, but does have positive feelings and attachments involved in the relationship to Kanmoo. also am not sure, but I do think Kangmoo holds some jealousy/possessiveness towards Kirin but maybe I’m misreading it
