in the beginning of 7th episode haej and jiho fight about seun. the scene is so odd!
haej has these behaviors that proofs he doesn't love her:
haej put seun on the floor and says to jiho: if you care about her, why do you let her on the floor? and right after, as jiho doesn't budge, he adds "how can a human neck bend like this" as seun is sliding slowly on the floor. then he agrees to let seun go to jiho's appartment, and eat chips while waiting for her to awake... when she awoke, he left right away.
these behaviors proofs he likes her:
he is happy she fell asleep on his shoulder, he hold her like a princess for quite a long time, he didn't want to let her lay in jiho's bedroom, so he put her on his couch.
his behavior says he likes her very much. I think she is his role-model. but he doesn't love her. in that matter, it's more important for him to make jiho mad than to earn points in seun's affection. everything he says and does targets jiho.
so my conclusion is, he doesn't love seun. maybe he is not aware of that, and genuinely thinks he loves her, but honestly, I doubt that. he is very much more aware of himself than jiho. he probably thought he loved her as long as he didn't see her, but since he met her in the flesh, I think he knows that he just admire her a lot.
that's also why I love this character. without him, jiho would have felt too secured and entitled as seun's husband to question his real feelings.