The story revolves around 15-year-old Rin Okumura, who, along with his younger twin brother Yukio, was raised by Father Shiro Fujimoto, an Exorcist. One day, Rin learns that he and Yukio are the sons of Satan. Witnessing Shiro dying to protect him, Rin draws the demon-slaying sword Kurikara, which restrains his demonic powers. From that moment on, Rin not only gains demonic features like fangs and a tail, but also the power to ignite into blue flames that destroy almost anything they touch.
Rin wishes to become an Exorcist like his guardian to become stronger and defeat Satan. He enrolls at the prestigious True Cross Academy exorcist cram school, which is actually the Japanese branch of an international organization dedicated to protect the human realm, Assiah, from the demonic realm, Gehenna. Much to his surprise, he finds that Yukio, is already a veteran Exorcist and is one of his teachers. Thus begins Rin’s journey to become an Exorcist, accompanied by his brother and his fellow students who quickly become his close friends.