Exactly you would communicate no I need you to reciprocate my feelings in order to date/ be in a relationship. Haewon may not have loved him romantically initially but he made a decision with intent to see Yun oh as a romantic partner. Yun oh whose prefrontal cortex can't process the decision as such is spiraling and not communicating his insecurities causing mistrust in their rocky relationship

For saying that's not love, Yun oh is not a communicative lil shit but also his prefrontal cortex is still developing so him being a dumb grown baby also makes sense
Run off in to the wild but make sure you reflect