The biggest headache of Rin’s school life is his daily meals. On Yukio’s advice, Rin starts cooking in the dorm kitchen, preparing lunch the night before. But in the morning, all the food has vanished!

Rin is always snoozing in class, much to star pupil Suguro's irritation. Suguro's striving to become an exorcist so he can restore his family's temple in Kyoto, and being classmates with such a slacker is more than he can bear.

When Yukio takes on a case, Rin tags along with him to the Exorcism Supply Shop. There he meets Shiemi, a girl with ailing legs, tending to her garden. Yukio examines Shiemi's legs and finding demonic traces, speculates that the garden is the cause.

Vowing to become an exorcist, Rin is taken to True Cross Academy by the mysterious Mephisto, a friend of their late father. Later, Rin heads to the Exorcist Cram School, as Mephisto warns: “You must keep that you’re the son of Satan confidential.”

Rin is thrown into turmoil when Shiro tells him that he's the son of Satan! Warning him that he must never draw it, Shiro gives Rin the Koma Sword, and hides him in the monastery basement. Outside, a fierce battle begins...

Rin Okumura begins to worry about his future as his twin brother,his twin brother, Yukio, is starting school at the prestigious True Cross Academy. Sent to a job interview by his foster father, Shiro, Rin encounters a demon-like creature and causes havoc in the store.