She is a handsome-looking girl with an unknown past, and he is a feminine-looking boy with powerful abilities. When she first came to this land from her hometown, he was the only one who recognized her gender, and they met. The bizarre suicide in the school, the enchanting man in the night sky, the ice-like woman, and her own unknown past will all be revealed. As a police officer, can he protect the safety of his beloved? And as the successor of the family's abilities, can she solve the crises before her? Who is she? Why does it exist? Where does the heart belong? What exactly is the agreement between sorrow and sadness? Everything is in "Sad Promise"