Kim Kibum (Key) 

The guy who Sooyoung adores and despises the most. The guy who would make girls swoon by his charming feline eyes, bow-shaped lips and the perfect jawlinee. The guy who nags like an ahjumma, dresses as if he's going to attend some kind of fashion show, walks as if everything he steps on is a runway, but is sweet and caring if he wants to.  He's also a multitalented person, he can sing, dance, rap, and act. 

Choi Sooyoung
One word, shikshin. She's being addressed as a shikshin since she tends to eat a lot but won't gain any weight. Has been crushing on Key for the past 7 years. Often fights with Key, and end up questioning her feelings for him. She could also sing and dance.