In the land of Ryoza, the neighboring provinces of Shin-Ou and Tai-Kou have been at peace. Queen Shinou is the ruler of Ryoza and her greatest general, Grand Duke Taikou, defends the kingdom with his army of powerful war-lizards known as the Touda. Although the two regions have enjoyed a long-standing alliance, mounting tensions threaten to spark a fierce civil war. Within Ake, a village in Tai-Kou tasked with raising the Grand Duke's army, lives Erin, a bright girl who spends her days watching the work of her mother Soyon, the village's head Touda doctor. But while under Soyon's care, a disastrous incident befalls the Grand Duke's strongest Touda, and the peace that Erin and her mother had been enjoying vanishes as Soyon is punished severely. In a desperate attempt to save her mother, Erin ends up falling in a river and is swept towards Shin-Ou. Unable to return home, Erin must learn to lead a new life with completely different people, all while hunting for the truth of both beasts and humanity itself, with tensions between the two regions constantly escalating.

Creatures known as Shokujinki have been secretly living alongside humans for hundreds of years. Though they may look like humans, Shokujinki are able to transform into uncontrollable beasts with gigantic claws and consume humans to survive. The equally secretive Kifuuken dojo specializes in killing Shokujinki by cutting off their arms, and is the only force preventing unchecked Shokujinki domination. Toshihiko Momota, the son of the leader of the Kifuuken, is instantly charmed by a mysterious woman named Yuka Kamitsuki. Their relationship is complicated, however, because unbeknownst to them both, Yuka is a Shokujinki and Toshihiko is sworn to kill her. Meanwhile, the Kifuuken is having a crisis of confidence as Toshihiko's brother Kazuma pushes against tradition and tries to modernize the Kifuuken. As emotions are strained and the secrets of both the past and present are revealed, who will live, and who will be eaten?

As Ayanokouji and his classmates begin their second year at the Advanced Nurturing High School, they're greeted by a fresh gauntlet of exams and a fresh batch of rather unique first-year students. They'll have to get to know each other quickly, because the first special exam pairs the first-years with the second-years on a written test—with only the second-years facing expulsion if their team performs poorly! Worse yet? It seems one of the new first-years is also from the White Room. Can Ayanokouji avoid expulsion while sussing out the identity of this hidden foe? (Source: Crunchyroll)

Adaptation of the Bugs 2 arc of the manga.