The modern-age medieval kingdom of Helianthus flourishes during an era of peace and prosperity, protected from the dangers of the outside world. However, this peace is interrupted when an appalling event befalls within the walls of the kingdom. The Dust Knights of the sovereign King Leopoldo are sent to uncover the truth behind the death of one of their own comrades, felled by an unknown killer. To protect their kingdom and avenge their brother, they will endure the worst.