University student Yuuta Segawa is minding his own business when his older sister asks him to watch her three daughters for a short trip, and then her plane goes missing. Rather than see fourteen-year-old Sora, ten-year-old Miu, and three-year-old Hina split up among relatives, Yuuta takes all three into his cramped one-room apartment. This light novel is the original source for the Papa no Iukoto wo Kikinasai! manga and anime, following Yuuta's crash course in parenting three very different nieces.