Flora, the daughter of the margrave of the western frontiers, returns from the battlefield only to have her engagement annulled by the first prince. He insults her as a worthless nobody from a family on the edge of civilization, a slight she finds more irritating than the broken engagement itself. Soon after, signs of a court conspiracy emerge, but a more immediate threat arrives from her territory: a demon invasion.

In response to this crisis, Flora follows the instructions of her Japanese ancestors and seeks help from a legendary dragon, intending to offer herself as a sacrifice. However, the dragon instead becomes her guardian and destroys the demon horde. The awakening of the dragon causes spirits to organize into legions and dramatically powers up Flora's purification magic. Realizing her territory no longer has any reason to remain subordinate to the kingdom that dismissed them, Flora declares independence and begins developing her lands freely.

The story follows the establishment of Drassen, the newly independent territory, as it rapidly grows into a powerful nation. Within a year, diplomatic relations are established with neighboring countries. When a prince Flora knew from childhood arrives by sea for negotiations, his ship is attacked by a wyvern. Flora and her dragon guardian Liber easily rescue him, and upon being shown the territory's vast farms and hot spring town, the visiting prince is astonished by its development. He becomes friends with Flora's brother Lias and enjoys spending time with the cat spirits, all while harboring complicated feelings toward Flora herself.

The setting is a fantasy world on the frontier of a kingdom, where civilization borders demon-infested lands. Flora's territory transforms from a dismissed backwater into a thriving, self-sufficient nation. Key characters include Flora, a saint and capable frontier lord; Liber, the legendary dragon who becomes her guardian; Lias, Flora's brother; and various animal spirits including cats, turtles, and seagulls who play active roles in territory development and protection.