Jiang Xin, a young white-collar worker who is inexperienced in the world, accidentally traveled back to the late Sui Dynasty and became the second young lady of the school captain's palace. She muddleheadedly entered the palace to accompany her sister who was a beauty. However, once she entered the palace, it was difficult to get out... As dynasties changed and the harem situation changed, how did she rely on her wisdom and luck to get around the world? How do the answers to each mystery surface? ... Her whole life, she was unknowingly entangled between Yuwen Shiji, Li Shimin, and Jiang Cheng, who looked exactly like her modern crush...