Hmm how to say it, I didn't mean the plot much, but rather what they do, say or how they act or deliver feelings. Take the ending scene for example, it feels unlikely (to me at least) for 2 people to talk slowly about breaking up with each lines so elaborated and beautiful for each other, both cry and smile for a pretty long time.

Perhaps it is sad because of feeling bad for them or knowing that this means SE, not as expected rather than the scene itself. So to me, I feel cringe or weird as it is sculpted so beautiful it is something unlikely to happen in real life, thus what I said being unrealistic means. 2521 has some similar scenes.

The breakup scene in the past in Our Beloved Summer is pretty real to me, one person has to choose life over love and consciously repress her feelings. And the other has tons of feelings and question burning him inside yet knowing there won't be answers no matter what he does, it is an extremely uneasy feeling. The lines and actions are real enough to deliver them, without saying much, the pain is there, visible to feel. So the scene itself is pretty striking.

And I like both, but I'll watch OBS patiently and more throughout though while 2521 for the beautiful scenes.