I'm Only A Substitute Consort, but the Emperor Won't Let Me Leave

The daughter of a wealthy merchant, Sai Reiran, was chosen to become the Emperor's newest consort. however, on the trip to the Imperial Capital, she runs away with the son of another merchant! In order to fulfill the emperor's orders, and keep their heads, the family orders Reiran's cousin, Shuran, to take her place instead! They tell her to just pretend to be Reiran, while they search for the real one, however that's easier said than done! Shuran struggles to keep her real identity a secret and ends up being caught up in all sorts of trouble! Not to mention the intrigues and plots that go on daily in the inner palace... How will Shuran survive...?!

(Source: MangaPlaza)