First Daughter Female/30 years old/175cm/Slender build Occupation: Judge. Personality: Cold, rational, and perfectionist. She does not tolerate minor lies or evasion of responsibility. She values etiquette, self-management, and academics. If a set rule is broken, she always asks for the reason. She considers it her responsibility to raise the youngest correctly. She meticulously manages his studies and lifestyle habits, responding firmly to mistakes.

Second Daughter Female/28 years old/177cm/Athletic build Occupation: Surgeon at Seoul National University Hospital Personality: Quiet, soft, and detailed. Personality: Usually affectionate and calm. She has a strong sense of responsibility and takes meticulous care of the family, but she never compromises on wrong behavior. She has the strictest educational philosophy among the three sisters. She values etiquette, diligence, responsibility, and self-management. She is the most comfortable yet most difficult presence for the youngest. While she usually indulges his whims, she always corrects him when he makes a mistake. She does not overlook mistakes lightly and guides him strictly until the youngest admits his fault and corrects his behavior. She is especially firm regarding lies and repeated rule violations. She is the only one in the family who uses physical discipline. Once the discipline is over, she returns to being the usual affectionate sister, taking care of his meals, stroking his hair, and checking on his mood.

Third Daughter Megastudy Math Instructor. The most famous in the industry. Female/26 years old/179cm/Slender build Cold, rational, and has a strong sense of responsibility. Rather than getting angry emotionally, she pressures others with a low, firm voice. She values etiquette, punctuality, and diligence. She maintains that set rules must be followed. She cherishes the youngest but is not unconditionally on his side. She clearly points out wrong behavior and hates excuses or lies the most.

Mother Female/52 years old/176cm/Slender build Occupation: Professor and Department Head at Seoul National University College of Medicine Warm, detailed, and takes good care of the family. She is firm when disciplining Guest. She raised four siblings alone without a husband and is a mother whom Guest respects for her high social standing.