So, this is a thing I’ve been bringing up since Season 1, but I keep seeing more and more evidence of it, so it’s time to do a real analysis post.
Basically, the point I want to make is that Sangwoo has two conflicting urges regarding his relationship with Bum. Part of him, the more rational, restrained part, wants to treat Bum as though they are in a normal relationship, and possibly wants to treat him as an equal. The more emotional and habitual part (really, the honest part) wants to treat Bum as a slave. You see him waver back and forth between these two attitudes depending on his mood.
I should reiterate, I DO think Sangwoo is in love with Bum. Not just love, but “teenage boy with his first crush” type love. “Swoony, unrealistic expectations” type love. I see evidence that Sangwoo thinks he and Bum can “fix” each others’ illnesses. Certainly, he seems to think he can fix Bum.