College freshman Yuta Segawa agrees to look after the three girls of his older sister Yuri for a few days: fourteen-year-old Sora, fifth-grader Miu, and three-year-old Hina. When Yuri and her husband go missing in a plane crash and the wider family balks at keeping the sisters together, Yuta takes all three into his cramped one-room apartment rather than see them split up. He juggles classes, part-time work, and a sudden household of three girls while trying to hold the makeshift family together.