Si-Yeon Yoon

Occupation: Student Do-Hoon's childhood friend and relative (as Do-Hoon knows it). They lived together since she was 5 years old and were always together. She grew close to him and wanted him all to herself which led to her making him an outcast at school. Then, in a series of bullying cases, Do-Hoon declared his independence and at the same time he made his wish to transfer, but they met again at the high school he transferred to.