Legend of Mercy is set in a fantasy world of sword and magic where a terrible and deadly plague is sweeping the land. However, this plague only effects the males of the races, while leaving the females unharmed. This has left only one male for every ten thousand females.
Besides this, the four races of the continent: humans, high elves, half-demons, and dark elves have split into two opposing alliances and have begun a war for the ages. With a population crisis and the ever-growing plague, the war has pushed the continent to the very edge of ruin.
As a doctor with incredible skill, you are called to this world by the goddess at this time of crisis. Accompanied by girls from both alliances, you are tasked to find a way to save the world together.