Sigyn

She is one of the members of GREMLIN sent to Baggage City for Othinus' experiment that was to take place there, and is the only one to have betrayed the organization after the prodding of the Kouga ninjas. Sigyn appears a fair-skinned woman with blond hair and blue eyes. Apparently the only member of GREMLIN who prepared for Baggage City's climate, Sigyn wears a red sweater under a white coat with a hood, along with white pants and shoes. She also wears golden necklace and golden headband.

(Source: Toaru Majutsu no Index Wiki)