Tae Ju is a salaried consulting medical doctor and planner for a medical documentary tv show. She is the eldest of three siblings and works as a professional liaison between doctors on the documentary and hospitals. As the oldest sibling, Tae Ju is warm-hearted and open-minded but has a short temper. She is Sang Jun's elementary school friend. Sang Jun has been a lead actor for twenty years and can act in emotionally diverse roles. Sang Jun, who once confessed his feelings to Tae Ju in elementary school, has a bright personality with dashing looks. So Rim and Gun Woo are Tae Ju's siblings. Will the K-eldest-son and K-eldest-daughter find happiness in their lives as they fulfill their duties as the eldest in the family while preoccupied with the burdens of life and marriage still ahead of them?