Capable of communicating with animals, Jirou Azuma, a troublesome 17-year-old high school student, is constantly scolded by his grandfather for fighting humans that harm his winged and four-legged friends. However, after Jirou saves a black cat named Ragou from certain death, his carefree existence soon comes to an end.

Unbeknownst to Jirou, Ragou is no ordinary cat but a mononoke, a magical creature of immense power. While trying to protect Ragou from another mononoke, Jirou is easily defeated and left for dead. In a dramatic turn of events, Ragou decides to pay off his debt to the dying young man, making Jirou a rare human-mononoke hybrid that easily overpowers his aggressor.

Unfortunately, Jirou is now sought by both Ragou's kin who want to use the latter's powers, and the Bureau of Espionage, a secret governmental organization protecting civilians against hostile mononoke. Forcibly enlisted by the Bureau of Espionage's Ryousuke Shiba, Jirou must prove his worth in a new anti-mononoke task force, lest he be killed as a menace himself.

[Written by MAL Rewrite]