After Yuuta spends the day with his three nieces, Yuri asks him to mind them while she takes a week-long trip with her husband, Shingo. While Yuuta looks after the girls, Yuri's plane crashes and she and Shingo are reported missing. Due to limited living arrangements, the girls' other relatives plan to split them up per but Yuuta intervenes and asks the three girls if they want to live with him.