Demons break into the monastery, targeting Rin. When Rin calls Shiro unworthy as a father, Shiro's hurt emotional state causes him to let his guard down and be possessed by Satan. Shiro gains control at the last moment and sacrifices himself to protect Rin. Upon seeing this, Rin fights back by unlocking his demonic powers with Kurikara, the sacred sword in which his powers are sealed. At Shiro's funeral, Rin meets Mephisto Pheles, who agrees with his wish to become an Exorcist to defeat Satan.

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.”

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.