The Letter From the Cloud Season 1 Episode 20

Shen Yu, the daughter of a corrupted official, marries into the Zhou manor. However, her "groom" Zhou Yue turned out to be a girl disguised as a guy. After revealing their secrets to each other, they decide to become sworn sisters and use their fake marriage in order to protect each other's identity. At the same time, Qi Zhang and Gao Mo, who are implicated by the case of Prince Rong, also begins to secretly investigate the case. The four of them work together to find out the truth.