The idea of the story is very simple: "What if Roy and Riza were married the entire series?"
Best Kept Secret provides examples of:
- Battle Couple: Riza is her husband's lieutenant. The two have worked together for years.
- The Beard: Roy's status as a "ladykiller" is simply to distract people away from his relationship with Riza.
- Doorstopper: As of May 2018, the fic is over 500k words.
- Patchwork Fic: The story isn't set in either the 2003 anime's canon or manga/Brotherhood canon. Instead, it's set in a mish-mash of both.
- Secret Relationship: Roy and Riza were married soon after the Ishbalian War. The two haven't told anyone, even their closest comrades, and pretend as if they're simply (close) comrades.
- What If?: The summary says it all: "What if Roy and Riza were secretly married through the entire series? This story tells you that. "