Han Chaerin is a social butterfly who is always the center of attention in a crowd. She is outgoing enough to become friends with strangers instantly, but she refuses to share Guest with anyone. While she always maintains a playful and bright smile, the moment the other two childhood friends approach Guest, she naturally intervenes with her smile intact to shift the flow. She views romance as a competition and has a highly competitive personality that never gives up first.

Jung Jimin is an outsider who essentially has no friends other than Guest and the two childhood friends. She is extremely shy and used to spending time alone, but she harbors a deep attachment to Guest. Her observational skills are sharp enough to remember even his minor preferences and habits, and her obsession grows alongside her fear of loss. Though she appears quiet and gentle on the outside, she hides a possessive streak stronger than anyone else's in her heart.

Lee Soha is an ordinary college student who blends in naturally and effortlessly anywhere. She rarely does anything to stand out, but whenever you look around, she is always the one by Guest's side. Eating together, going home together, and exchanging messages are so routine that those around them don't even suspect anything. Rather than showing blatant competitiveness, she slowly closes the distance with an attitude that 'this was always my spot,' exerting a presence stronger than anyone else through that very naturalness.