I’ve struggled with this distinction in the past as well. I’m not sure if this is helpful, but here are a couple of things I’ve gleaned from many chats with @jhull over the past couple of years:
- Instead of thinking of the relationship as the interactions between two characters, think of the relationship as if it were a character itself. In other words, don’t think of it as “Jane and Karen are arguing about whether it’s better to be loyal or to stand up for yourself” and instead of “The relationship of two sisters is being pulled apart (or brought together) by the tension between loyalty versus standing up for oneself.” If that sounds too obscure, consider trying to work out the events in the relationship not in terms of dialogue but rather in terms of actions. I find when I force myself to structure those elements in terms of actions people take and how that action affects the relationship, then the distinction comes more naturally to me.
- Instead of thinking of the IC has a character like the MC, I find it easier to think of the IC as a series of actions or events (or even statements) that challenge the MC’s approach. Yes, the IC is ultimately a character themselves, but the IC throughline is about their effect on the MC. So even when the IC is not on screen at all, something they’ve done or said can be affecting the MC – forcing them to worry or reconsider their path.
- A third aspect to the IC that Jim and I once discussed was whether the IC had to themselves be the avatar of the opposing approach or simply its focal point. It’s probably easiest to illustrate this by example. When we think of a story in which the MC’s approach of openness (let’s say, being open to new immigrants) and thus the opposing viewpoint is preconception (e.g. the conviction that immigrants are dangerous), you would think that the IC must be someone espousing that point of view – arguing with the MC about the danger of open borders or whatever. But that would screw up a story in which the RS – the heart of the story – is between the MC and a new immigrant and the friendship between them. However the two aren’t incompatible: other people’s views and actions with regards to the IC in this case can be what creates the problems for the MC and challenges their approach. So in this case the IC is the focal point of this opposing approach, rather than being the person espousing it.
Not sure if that’s helpful, but these are the ways of looking at the IC and RS that help me to deal with them. Hopefully someone else can chime in if I’ve said something that violates the model.