Two kingdoms exist in the heavens, each with their own royal families. Despite being at war, a prince of the Black Country, Sakuya, is friends with a prince of the White Country, Rui, and his sister Mio. The three spend a lot of time together at a lake on neutral ground. One day, Mio frantically flew to their spot and called out to the boys, but was drawn into a strange portal and disappeared into darkness before saying anything. Left behind, Sakuya and Rui are still drawn to the location. Three years later, a girl dressed in foreign clothes who looked exactly like Mio fell out the sky. However, she claims to be a different person from the lower realm!? (Source: shinkeikaku)

Since her mother's death and her father's remarriage, Sarah, the daughter of an earl, has been bullied by her stepmother and stepsister. One day, due to the whims of her stepsister, who married into the royal family, Sarah ends up switching places with her and playing the role of the prince's wife. She had heard that prince Sirius was cruel and didn't even look at her... This is a marriage love story that begins with a body swap and ends if it is discovered! https://www.cmoa.jp/title/295429/