Set at a prestigious private high school in Gangnam, Seoul, South Korea. Eun-Byeol is a popular student at the private high school. She goes missing and returns, but she has lost her memory. She tries to find out the truth.
Lee Eun-bi lives at the orphanage Love's House in Tongyeong, South Gyeongsang Province, where younger residents look up to her as a mother figure. They don't know that she's friendless at her school and viciously bullied by a posse of mean girls led by Kang So-young, while teachers turn a blind eye.
On the other hand, Go Eun-byul is the most popular girl at Segang High School, the most prestigious private high school in Seoul's Gangnam District. Eun-byul's best friends are Cha Song-joo and Lee Shi-jin, and she shares a mutual attraction with Han Yi-an, the school's star swimmer. But Eun-byul has secrets, including one involving a girl named Jung Soo-in.
Eun-bi and Eun-byul look exactly alike, but only Eun-byul is aware of the other's existence.
One day, on a school field trip to Tongyeong, Eun-byul mysteriously disappears. At the same time, Eun-bi gets unjustly expelled from her school and transfers to Segang. Mistaken for her doppelgänger, Eun-bi soon succumbs to the temptation of pretending to be Eun-byul and living the latter's charmed life.
