Hyeri as Sung Duk-seon/Sung Soo-yeon The middle child of her family, she is infamously ranked 999th in school and is the only girl in their group of five neighborhood friends.
Lee Hyeri sebagai Sung Deok-sun/Sung Soo-yeonAnak kedua dari keluarganya, dia terkenal peringkat 989 di sekolah dan merupakan satu-satunya gadis dalam kelompok lingkungan mereka.