The Spy Who Married Me

A kingdom sends two sisters across the border as brides in a peace treaty, and everyone at the receiving court assumes the marriages are cover for espionage. Jill Shaw wakes up in the body of the elder sister on her wedding day, already promised to Prince Joseph Smith, a general the enemy troops call the god of war. Her modern best friend Helen Stone wakes up as the younger sister, married that same day to Joseph's brother Prince Ben Smith, a man known at court for getting what he wants through charm rather than force. Both brothers go into the marriages convinced their wives are trained agents and prepared to act on that conviction. Joseph keeps Jill under constant watch, waiting for her to slip. What he finds instead is a woman who has a doctorate in strategic studies back in her old life and cannot help herself around a bad defense map, staying up rewriting his troop deployments and correcting his supply routes because the numbers bother her, with no interest in his secrets beyond whether they add up. Ben takes the opposite approach with Helen, treating her as an easy mark, a girl who fell for him too fast to be dangerous. Helen ran an online following before she transmigrated, mostly for reading people and giving advice on relationships, and she recognizes every move he makes before he finishes making it. Within weeks he is the one waiting on her attention instead of the reverse. The sisters start pooling what they know, setting up a small trading venture on the side and using it to trace money moving through the palace that neither prince has noticed. Joseph begins asking Jill's opinion before councils instead of wat