Academy city a place we're the brightest of the brightest come to become espers and for some to have a better future. Misaka Mikoto the third rank level five in academy city and the Ace of Tokiwadai reserves a package from her mother with a note saying she found some things that belong to some distant relatives they lost in touch with while looking threw there attic so she thought she might enjoy them. When she opened it all there was were a few weird books, a small chunk of some mineral and a rock with some kind of red fluid on it and lastly a vile of mercury. With her roommate they read one of the books but what they didn't know is that action set off a war they would probably couldn't believe.