The short answer
Follow the relationship itself: what brings it together, pulls it apart, or changes what it means to the people involved.
A friendship becoming a rivalry gives you something to track beyond each person’s private struggle. Ask what is happening to the friendship and why. This makes it easier to distinguish the Relationship Story from the Influence Character’s effect on the Main Character. The same scene can carry both. A Relationship Story does not have to be a romance.
An imagined example
A friendship under pressure
Two lifelong friends open a restaurant. When one secretly accepts an investor, their friendship becomes a business arrangement full of conditions. Beyond either friend’s private fears, track how trust, closeness, and obligation change between them.
Try it in your story
Describe the relationship at the beginning and the end without listing either person’s private problems.
Where this answer comes from
An editorial synthesis of these discussions. The example above was written for this answer.
- Question about Relationship Throughline
Jim Hull, December 9, 2016, post 7.
- Distinguishing between IC and RS throughlines?
Sebastien de Castell, May 26, 2017.
- Relationship throughline
June 2020, especially John Dusenberry’s posts 2 and 9.
A note on older terminology
Older discussions may say Overall Story for Objective Story, Obstacle or Impact Character for Influence Character, and Subjective Story for Relationship Story. Source titles retain their original wording. Historical software instructions describe the tools of their time.