Yeonwoo's and Junhyuk's relationship is an incredibly interesting portrayal of a toxic relationship.
In almost any manga/manhwa you see a toxic relationship will always be abusive, and that's the toxicity.
But in this manhwa Junhyuk is not only actively manipulation/gaslighting Yeonwoo which is rare itself, but he also clearly cares and cherishes Yeonwoo.
Becuase of this, the relationship is more than just multifaceted, it's realistic.