Yuuta Segawa, a 19-year-old college student, finds his life turned upside down when his older sister and her husband tragically pass away in an accident. Left as the sole guardian of their three young daughters—14-year-old Sora, 10-year-old Miu, and 3-year-old Hina—Yuuta must navigate the challenges of suddenly becoming a father figure. Despite his inexperience and the overwhelming responsibility, Yuuta is determined to provide a stable and loving home for the girls.

The series explores the daily struggles and heartfelt moments of this unconventional family as they adjust to their new lives together. Sora, the eldest, initially resents Yuuta for taking on the role of their guardian, feeling that he is unfit to replace her parents. Miu, the middle child, is cheerful and optimistic but often hides her own insecurities about the family’s situation. Hina, the youngest, is innocent and unaware of the complexities of their circumstances, bringing lightheartedness to the household.

As Yuuta balances his studies, part-time job, and parenting duties, he receives support from his childhood friend, Raika Oda, who helps him care for the girls. The narrative delves into themes of family, responsibility, and resilience, portraying the emotional growth of both Yuuta and the girls as they learn to rely on each other. Through moments of humor, sorrow, and tenderness, the series captures the evolving dynamics of their relationships and the challenges of building a new family in the face of loss.