
Alex still have his own fault in all this. 1. he choose a sex friend with someone he know he adore him! and he took care of him while he was drank! that not what people that not in love DO! so Alex know, he just choose to ignore it. throwing the blame over to DG that clearly could admit he love someone that will leave him. it was crual of him to even ASK!!
2. Alex got super possessive or jealous over DG, what again gave DG faulse hopes he love him somehow. what again is Alex fault! and of course he rape him for it and then go with him for a date! if he really care that much, he should have break it off by himself, since the control was all his, a long time ago!
3. sex friends have much respect with each other then how Alex ever treat DG!!! ever!!! so yeas, they never really was a real sex friends.

First of all: I did this topic only with my opinion of Dong Hyun.
1. Remember that the character doesn't "see" everything we see as readers, so even if for us is totally obvious that DG is in love with Alex is not the same for him, sure DG's behavior would make anyone suspect that he is in love with Alex, but there is a gap to go from suspecting to be totally sure and the only way to be totally sure about someone else's feelings is to listen to the person himself say it out loud, so even if Alex suspected that DG could have feelings for him he still needed to make sure by listening to DG himself so that's why him and anyone who decided to take the right decision would do in that situation is to ask, so he did, it wasn't cruel of him it was mature and right of him to ask, and even having the other person giving him the perfect oportunity to come out clean DG decided to keep puting himself in that hopeless relationship. People are not the ones to blame if you decide to put yourself in hopeless relationships, they are not the bad ones for not reciprocating your feelings.
2. Yeah getting possesive over DG that could lead him to having a little bit of hope was he's mistake but he made things clear again by remembering DG that he is not interested in a lover. The date is not Alex's fault, DG was the one asking for it and in the situation he used to ask, it was obvious Alex would agree (that is exactly why DG asked, in any other scenario Alex would reject him right away).
3. I don't understand very well what you tried to say in this one. Sorry.

1. read the first and second chapter, DG admit to Alex from the very start that he admire him without known it was Alex. so no, and if someone taking care of you while you drank all night, YEAS they love you! it only COMMON SENSE! so no, stop justify Alex crap saying he didn't know! he did know, he sew how DG was in their "date" he fucking know! but choose to ignore it! he didn't need to make sure anything, his actions speak louder then words! of course DG won't say anything, known the person he love will LEAVE him if he admit it! that what Alex did to make sure he won't say anything.
2. geez really? I thought you going to justify that too. no he did a mistake by staying and keep living in deny of the fact that he did LOVE DG! while saying he didn't want relationship. if he really didn't want a real "Relationship" he should have cut it off when he sew he felt possesive cause no, that not how you act to someone you don't care about! it is Alex fault cause he fucking RAPE HIM over jealousy he had no right to even have!! and taking his anger on DG. and no Alex could have say no and break it off from there but he choose not too. again he only care about himself and not DG feelings!
3. friends don't treat each other like crap or slave like Alex did to DG. to have sex take two not one. simple has that. so they never act like "sex friends" ever ╮( ̄▽ ̄)╭
Even though I feel bad for Dong Gyun truth is that he seeked this upon himself (no, I'm not talking about Alex hitting him). Dong Gyun said "you don't think about how I feel" to Alex and that's not true, Alex did think about him when he gave him the chance to be honest about his feelings, Dong Gyun was the one who decided to lie and believe in a relationship that doesn't exist all by himself, he is the one blurring the lines of "just sex friends" that he agreed to, TWICE. He complains that Alex just calls him when he wants to have sex and well... yeah, they are sex friends, that is what a sex friend is for, again he is the one blurring the lines and expecting something when it was left clear that he shouldn't.
Even though he must be feeling awfull it doesn't justify what he did (interrupting the show and almost exposing himself and Alex with all the consequences that could bring), when you bottle up feelings like that usually the outcome is really bad because you take rash decisions and lash out.