Haruka Momo 
The Engagement of Marielle Clarac (Manga) Volume 5 [EPUB ebook] 

With spring just around the corner, all Marielle can think about is her upcoming wedding—that is, until she’s rudely awakened from her daydreaming by the shadows of doubt and intrigue creeping into her life. It all starts when she meets a mysterious gentleman during a kerfuffle involving the navy in the middle of the city, and her consternation compounds from there when she finds out that Simeon has been arrested on suspicion of leaking state secrets. Something is afoot, and Marielle is determined to find out what in order to clear her husband-to-be’s name!