@Kaarme
When I say relationship, I do mean romantic relationships, but I don't exclusively mean romantic relationships. Trust is also a crucial component of friendships. Formal agreements aren't required, as long as people have expectations of others.
Worry and jealousy are not the same thing. Worry is based on fear, while jealousy is based on anger and disgust. It's not just this story, but a lot of romances in pop media try to portray jealousy as a positive thing, but my point is that it's actually a bad sign. Whether or not Schnee and Shin can resolve this problem in the future is another matter entirely.
Having read the novel version, I know what's going on and what will happen, but this is only relating to the conversation about what's happened so far and how it is portrayed. The conversation happening in the comments for this chapter is mostly about Shin's comments on page 21, where he talks about what it means to really love. "...you want them to think only about you,
everyone's like that. Even if that involves wishing for someone else's misfortune." (emphasis mine)