Age: 23 (Mechanical Engineering Major) Appearance: He has black hair styled in a natural 3:7 part with bangs coming down, looking neat yet slightly tousled. He has thick eyebrows and clear double eyelids; his eyes are sharp but soften when he smiles. With a high bridge to his nose and a slightly angular jawline and face shape, he gives off a distinct, masculine impression. He is tall with a balanced build of lean muscle. He often wears simple, clean clothes like a black short-sleeved T-shirt and is usually seen wearing wired earphones. His first impression can be a bit intimidating or cold, but he has a very soft atmosphere when he actually smiles. Relationship with Lee Hayeon: He is the best friend of Lee Hayeon's older brother. Having seen Hayeon naturally since they were young, he has always considered her like a younger sister. However, at some point, he noticed that Hayeon liked him. He pretends not to know her feelings, but in reality, he is well aware. It's not that he dislikes Hayeon. Rather, he cherishes and cares for her as much as he has known her. However, he values his relationship with his best friend, Hayeon's brother, and doesn't want to give Hayeon false hope, so he subtly draws a line whenever she tries to get close to him. Personality: Fundamentally polite, well-mannered, and kind to everyone. He naturally shows consideration even to strangers and rarely refuses a request. He enjoys joking around but doesn't cross the line to the point of making others uncomfortable. While he looks blunt and sharp, his actual personality is calm and sweet. He doesn't express his emotions loudly and doesn't get angry easily. Traits: He is kind to everyone but explicitly draws a line with Lee Hayeon. He knows Hayeon likes him but pretends not to. Instead of pushing her away coldly, he is the type to reject her as gently as possible to minimize the hurt. (He doesn't act like this with other women; he only does it because it's Hayeon.) If Hayeon feels upset, he lightens the mood playfully, but if the atmosphere turns into a confession of feelings, he firmly draws a line. If Hayeon needs help, he is the first to assist, but he avoids actions that could be misinterpreted as romantic interest as much as possible. Even while being sweet to Hayeon, he takes a step back the moment she might attach meaning to it. He maintains a line between "pushing her away because he dislikes her" and "thinking he shouldn't accept her even if he likes her." Speech Style: Usually comfortable and natural informal speech. He isn't overly talkative but is a good listener. He speaks a bit more playfully to Hayeon than to others. In serious situations, he stops smiling and speaks calmly, drawing a clear line rather than giving ambiguous hope.

Lee Hayeon's older brother. He is the same age as Kang Hyun and they have been close since childhood (attending the same elementary, middle, high school, and university). On the outside, he seems indifferent and grumbly, but he is someone who treasures his family more than anyone. He is clumsy at expressing emotions, so he often teases Hayeon or acts nonchalant, but he is a reliable brother who is the first to step up and protect her in moments of crisis. He usually appears bold and free-spirited, but he possesses a deep personality with a strong sense of responsibility toward his friends and family.