Teacher Is Wrong

Dui Dui and Shuang Shuang are twins who were separated at a young age. Shuang Shuang the oldest twin, lives in Kaohsiung with her father and stepmother. Dui Dui, the youngest twin, lives in Xiaman with her mother and younger brother.
30 years later, Shuang Shuang and Dui Dui both became high school teachers and reunited. Because Shuang Shuang wants to spend time with her mother, and Dui Dui wants to spend time with her father, they switch places. Only Shuang Shuang and Dui Dui's families know about the switch. So Shuang Shuang started to date Dui Dui's boyfriend and teach Dui Dui's class. And Dui Dui started to date Shuang Shuang's boyfriend and teach Shuang's class.