The main characters:

Tania Prince (OC) 17

Jesse Greene (OC) 17

Jiyong Kwon (18)

Seyong Kim (18)

Kim Myungsoo (17)

Do Tatsuya (19)

Hyuna Kim (18)

Suzy Bae (17)

Yang Hyun Suk (47)

Jin Young Park (46)

Soo Man Lee (46)

And some cameo characters....