She is the eponymous character of Toaru Majutsu no Index. Commonly known as Index, she is the main female character of the Magic Side; in Toaru Majutsu no Index series. She is a member of Necessarius and has Perfect Memory and is not poisoned by the effects of reading grimoires. As such, she holds within herself 103,000 magical grimoires at the beginning of the series.
Index looks like she is 14-15, one year or two younger than Touma. She is small in stature, has a petite build, and, much to her chagrin, a flat chest. She has thigh length, silver hair, and large green eyes. She is also often seen wearing her Walking Church, a white, and modified nun's habit with gold highlights. It is an accurate replica of the Holy Shroud of Turin and offered Index ultimate protection from most attacks, however, it was destroyed by Touma's right hand. She still wears it, though safety pins are now needed to hold it together.