On the day she turns 20, Hiyori Izumo, who lives in a poor village, marries Saku, the head of the Minazuki family, who is seven years older than her, according to the village tradition that "children with a sun birthmark marry into the Minazuki family." Despite the semi-forced relationship, Saku is strangely welcoming to Hiyori. The sweetness and magnitude of Saku's love for Hiyori is too much for Hiyori, who hasn't even found her first love yet... A drowning married life full of inexperienced stimulation!