
don't get me wrong, i love the kiss too. but isn't kang jinha being a bit fast and childish? like, he sees si won again and is in love with him, but immediately expects a response. i feel as if he shouldn't have brought up the kiss and just realized "hey, si won doesn't have to like me like that right away. we can start off as friends again because he really seems to care." give me your opinions and explanations cuz this is kinda nagging at me.

i wish the last panel was a picture of them together with the rings and holding hands. that would've made it feel more complete to me.

They have that here
http://www.mangago.zone/read-manga/graduation_certificate_artbook/

But doesn't Bum not love Sangwoo anymore?

I don't think Bum has every questioned why he was attracted to Sangwoo. He liked the affection Sangwoo gave him and is trying to convince him self that he did not love him. He thought of the affection Sangwoo gave him and was constantly telling himself it was not love he felt in those moments. The thought process Bum had in 15 is very contrasting the thought process Bum had back in chapter 1 where he'd constantly justify his own actions "because of love" even when those he obsessed over got hostile. Bum was having an internal conflict between how he felt about the idolized Sangwoo he obsessed over and the real Sangwoo who has abused him. He was so torn between his feelings and I don't think he was as able to fully convince himself that he no longer loved him.
ooOOOOH bABY! That final sex scene gives me LIFE!!!