The neighboring provinces of Shin-Ou and Tai-Kou in the land of Ryoza have enjoyed a longstanding alliance, maintaining peace under the ruling Queen Shinou and the protection of Grand Duke Taikou and his army of powerful war-lizards, known as the "Touda." However, mounting tensions threaten to ignite a civil war. Erin resides in Ake, a village tasked with raising Grand Duke Taikou's army in Tai-Kou. She spends her days observing her mother Soyon, the village's head Touda doctor. One day, disaster strikes when the strongest Touda under Soyon's care is harmed, leading to severe repercussions for her mother. Determined to help, Erin ends up being swept away in a river and lands in Shin-Ou, where she is forced to start anew with a different group of people. With escalating tensions between the regions, Erin must navigate her new life and seek to uncover the truth about beasts and humanity itself.