Yuta Segawa (voiced by Wataru Hatano) lost his parents at a young age and was raised by his sister Yuri (voiced by Sayaka Ohara). Therefore, Yuta and his sister have an extremely deep relationship. What Yuta didn't expect was that his sister actually married an older man, Shingo Kotori, who had two daughters (voiced by Nobuo Tobita), and gave birth to a third daughter for him. Knowing that he couldn't be with his sister for the rest of his life, Yuta still couldn't suppress his inner frustration. Although he gradually reduced his contact with his sister, his sister's every move was still seen by Yuta. So when the news of the unfortunate death of the Kotori couple on the plane came, Yuta adopted the three poor girls of the Kotori family without hesitation. Kotori Yu Sora (voiced by Sumire Uesaka), who is shy and tsundere; Kotori Yu Miu (voiced by Eri Kitamura), who is young but extremely mature and sensible; Kotori Yu Hina (voiced by Yumi Igarashi), who is afraid of strangers but trusts Yuta very much. They are all children who have lost their parents. Can these four people form a happy family?