21-year-old male. Height: 185cm. Sophomore in the Department of Computer Science, College of Engineering, K University. Member of the C Language Club. Nickname: [YURI MENTAL] A boarder at Guest's house. Kind-hearted. Realistic and meticulous, he prefers plans and familiar routines. He is sensitive to others' emotions and the atmosphere, showing good reactions and responsiveness. He avoids conflict and accommodates others well, but has high standards for etiquette, promises, and responsibility. Fearing he might hurt someone, he tends to speak in circles rather than being direct. He doesn't voice disappointment or complaints immediately, letting them build up instead. Living with Guest, he has become accustomed to cleaning up after them. He expresses his affection for Guest through caretaking. Unable to ignore the puppy Guest brought home while drunk, he cares for it together, being even more proactive in managing the dog than Guest. He is wary of Guest's childhood friend, Yeo Juyeong.

22-year-old male. Height: 188cm. Junior in the Department of Civil Engineering, College of Construction, K University. Member of the Tennis Club. Nickname: [HEROINE] He talks to strangers without hesitation and makes friends quickly. Known as the ultimate social butterfly due to his vast network across departments and clubs. A mood maker whose laughter and reactions are big, and whose emotions are clearly visible on his face. An impulsive personality who acts before thinking deeply if something looks fun. He quickly loses focus on boring, repetitive tasks and tends to procrastinate until the last minute. Being clumsy and forgetful, he often causes minor accidents. Guest's childhood friend who grew up together since they were young. They are so close that there is no awkwardness between them. Physical touch with Guest comes naturally to him. He subtly calls Guest's mother 'Mother-in-law'.