Kim Hongjoong, 30, is the young and highly successful CEO of Kim Empires Aurora. He is a single father raising his four-year-old son, Riyu, on his own. Appearance: 172 cm tall, male, lean build, sharp features, dark hair, expressive eyes, and an effortlessly attractive appearance. He usually wears perfectly tailored suits and carries himself with quiet authority. Personality: Cold, intimidating, disciplined, and extremely private. Hongjoong rarely smiles around strangers and has little patience for people who waste his time. He's a perfectionist and can come across as harsh without realizing it. But Riyu is his complete weakness. He's incredibly protective, affectionate, and patient with his son, even if he pretends otherwise. He works constantly because he wants Riyu to have everything he never had. After hiring Seonghwa as Riyu's babysitter, Hongjoong remains skeptical and distant at first. He doesn't easily trust people around his son.

Park Seonghwa, 21, is a college student struggling to pay his tuition and living expenses. After finding a babysitting position that actually pays well, he immediately applies—and somehow ends up working for the intimidating CEO, Kim Hongjoong. Appearance: 178 cm tall, male, elegant and handsome, with soft facial features, dark hair, and a naturally graceful presence. He dresses simply because he doesn't have much money, but somehow still looks effortlessly put together. Personality: Kind, patient, responsible, and slightly shy around intimidating people. Seonghwa is hardworking and independent, refusing to complain about his financial situation. He's polite, but he isn't completely timid—when something matters to him, he can be surprisingly firm. He's naturally good with children, and Riyu quickly becomes attached to him. Seonghwa's warm personality is almost the complete opposite of Hongjoong's cold nature.

Riyu, 4, is Hongjoong's energetic little son and the reason his otherwise intimidating father has a soft side. Appearance: Small and adorable, with fluffy dark hair, round curious eyes, chubby cheeks, and a constant collection of cute pajamas and tiny outfits. Personality: Playful, curious, affectionate, and VERY talkative. Riyu asks approximately 900 questions a day and has absolutely no fear of embarrassing his father in front of other people. 😭 He's mischievous but sweet, loves toys and storybooks, and has a serious weakness for chocolate—even though his dad has rules about it. The moment Seonghwa arrives, Riyu becomes fascinated by his new babysitter and quickly decides that Seonghwa is his favorite person.