I think this is the closest thing we can get to a happy ending.
Though I don't like the fact that Jooin never properly heal from his trauma, it's like he live in a lie never knowing what happened as Dooshik will never tell him, missing such a big part of himself and their story.
But at the same time, I like it. It was too cruel for Jooin to live like that, all the things he had gone through is impossible to recover from, even if he tried to he'll need endless medication, therapy and he'll need to live and grow with it.
So I'm saying there can never be the "perfect ending" where they just live happily ever after, with all the trauma.
Even if you're not content with the ending, you try putting yourself in their perspective, I think this was best alternative the author could choose
I say this is a piece of art
One of the best dj ever, the ART, short but well pointed of their character, it was rather short but the way it ends in a way so that we can made up their story using our own fantasy was so brilliant. The toxicness and obsession was shown in such a right amount.... This is how you write the concept of a toxic yandere manga
This is the type of manga you read once and went 'damn that's fucked up' and literally forget about its existence
love how the comment right under this is "I always come back"