The trust problem at the heart of the genre
Spy romance is built on a structural paradox: spies are professional liars, and romantic love requires a quality of honesty and vulnerability that professional lying is specifically designed to prevent. This is not a problem the genre works around; it is the problem the genre is about. Every element of the spy romance should be working with this paradox rather than despite it. The cover identity, the classified mission, the inability to tell the truth about where you go and what you do: these are not obstacles external to the relationship but features of who the spy is. The romance succeeds only when both arcs reach the same question at the same time: can this person be known, and if they are known, will they still be loved?