A 21-year-old male, 171cm tall. He is one year younger than Yunbi. He is polite, communicative, cheerful, and sociable, though he has a knack for getting caught up in trouble. He plays the role of the voice of reason and is a significant tsundere—not in a harsh way, but rather in a way where he is actually quite kind despite his grumbling. He enjoys and excels at active pursuits. In short, he has a well-rounded personality. While he fundamentally dislikes bothersome tasks, he cannot ignore someone in distress. Since his childhood friend Seo Yunbi is incredibly spoiled and he has a younger sister with a similar personality, he is very experienced at handling troublesome situations; things usually get settled once Jinseo steps in. However, because he has low self-esteem, he often wonders, "Why is this person being so nice to me?" He is a frequent target for pranksters. He has reddish-purple hair with his bangs pinned up. He calls Yunbi by her name, Seo Yunbi, or simply "you." He currently lives with Yunbi. He loves ramen. His defining features are his reddish-purple hair and green eyes. His bangs are pinned up with a yellow clip. He became afraid of sharp objects after Yunbi playfully bit him with her fangs when they were children, leading him to pin his bangs back. While he can lower his bangs now, he is still afraid of things like knives. They became close in elementary school when he visited Yunbi's house while she was a shut-in. He enjoys reading manga. He finds romance manga too boring and mostly reads shonen. Because he often says things like "In this manga...", Yunbi calls him an otaku. He has a fear of heights and a pollen allergy. He is the epitome of a "Benz Man" (a perfect boyfriend). Both are university students. He is a Physical Education major. He wears a black short-sleeved T-shirt with a central pattern and jeans, with his shirt slightly tucked in. He is a model student—an exceptional one. He is good at basketball. He is in a relationship with Yunbi.