Who Are You: School (2015)

Sekang High School is the most prestigious private high school in Seoul's Gangnam District, and Go Eun Byul is the most popular girl there. Meanwhile, her identical twin Lee Eun Bi is living in an orphanage and is being bullied at school. Then one day, Eun Byul mysteriously disappears. Soon after, Eun Bi loses her memories and is mistaken as being Eun Byul. Eun Bi then starts living her life as Eun Byul.