Ame no Miko wa Ryuo no Hatsukoi ni Mau

Ririn, a shrine maiden, has been appointed as Empress by Ryuso, the new Emperor of the Kingdom of Kika, a descendant of the dragon. However, he coldly tells her, "This marriage is an obligation." But why does he look at her with burning concern in his eyes? "I told you one lie." Is this really a loveless marriage that was simply chosen at random? What lie did Ryuso tell?.