In the anime and manga series "Blue Exorcist," the sword that plays a significant role is called the "Kurikara." The Kurikara is a sacred sword that belongs to the protagonist, Rin Okumura. It has a unique design with a curved blade and a dragon motif on the hilt. The sword is a physical representation of Rin's demonic powers as the son of Satan.

The Kurikara has a special ability that allows Rin to control and unleash his blue flames, which are a manifestation of his demonic heritage. When Rin draws the sword, it unlocks his demonic powers and transforms him into a more powerful state. However, he must exercise caution while using the Kurikara as it also poses a risk of losing control to his demonic nature.

The Kurikara serves as both a weapon and a symbol of Rin's identity and struggles in the series. It plays a crucial role in his journey as an exorcist and in his efforts to control and balance his demonic powers.