In a world where science clarifies supernatural powers. In a huge college that has power development in its curriculum. To a resident high school student, Kamijou Touma, a pure white sister appears. She calls herself "Index" and says that sorcerers are chasing her. Thus, Kamijou Touma enters the world of the occult.
One of the best anime series of all time in my opinion. It is simply mind blowing especially once you get into To Aru Majutsu No Index II. There is also a movie and a side series To Aru Kagaku no Railgun and Railgun S.
I highly recommend the main series and the movie, the side series is also fairly good.
you can dig up the full novel translations online if you really enjoy the series which i highly recommend.