You are probably have issue of being overly sensitive.. the protagonists chose each other, (not the readers chose to ship them regardless). . If one is abused and even though chose to be a relationship with the abuser after they sorted out their misunderstanding and issues (which is kinda lacking here, a proper conversation between them, that is) and by the course of time developed a loving and caring relationship, you are not supposed to have a problem with that..
People are just happy and being hopeful with the fact that the events of continuous misunderstanding and suffering is now ended with them realizing their follies and stepping forward to a better themselves.. and you call those ppl "mentally ill" lol,, yeah they should obviously have been happy if only the ending were with both the MLs being suicidal and killing themselves, no?
And as for me, my first comment sarcastic which you failed to realize, which was why I replied you with quotation mark but you didn't grasp it..
it's okay I'm not gonna be disrespectful to your opinion bt again I have to agree to disagree bcz I'm in that line of eternal hopeful ppl..
the "positive" impression that some of you feel for the ending is just "fake happiness" because it's not really a happy ending dohyun and seungho unconsciously long for warmth and human relation (especially dohyun) that they're willing to stay in a toxic and dangerous relationship wherein there's no guarantee that both of them would live to see the next day