A member of an American family of En-Jutsushis, specially skilled in creating and controlling spirit beasts to harness flames. She manipulates myriads of spirits into a single virtual persona to grasp tremendous power. While seemingly capable of creating different spirit beasts, her favorite is Metatron, an angel-like statue equipped with a sword. Kazuma has observed and mentioned that her fighting style is similar to Ayano's, referring to their simplistic and direct attacks, which lack any strategy or tactics. A rival against Ayano in both En-Jutsushi and Kazuma's "love". (wikipedia) When her first battle with Ayano doesn't go as expected, Katherine hires Kazuma to train her in developing more advanced fighting moves, and quickly becomes attracted to him. She then realizes that if she can pay him more then the Kannagi family does, he'll be willing to go back with her to America, so she often temptes Kazuma with lucrative offers.
After Katherine loses to Ayano a second time, she decides to stay in Japan for awhile in the hopes of convincing Kazuma to go with her to America. She later assists the police with capturing rouge magic users and becomes an honorary detective.