A clan of monsters that have existed since the Asuka period and protects the emperor from evil beasts called "monsters". Until now, they have continued to secretly fight fierce battles with monsters. The demonic beasts that resisted the Youbu clan evolved by absorbing human knowledge, and some of the demonic beasts that acquired cunning created an organization called the Grudges and tried to take over the human world. A battle for the fate of two races, humans and beasts. What is in its path...?