The Crimson Flower that Divides: Lunar Coupling

A fatal disease has left women scarce across the land. In the southern country of Ruse, a girl named Naala lost her mother to a raid by the northern country Nasula when she was still young. The one who stood by her through those dark years was Olli — her adored older brother figure and childhood friend, destined to be the next king. Years later, Naala has been adopted into the royal family and is living peacefully as Olli's fiancée. Then Nasula's army strikes again.