The To Aru Kagaku no Railgun side story is based on Kamachi's original story set in Academy City, a city where about 80% of its 230,000 citizens are students. The story deals with the adventures of Misaka Mikoto, one of the Level 5 psychics in the To Aru Majutsu no Index light novels
Possibilities never end, this anime is really worth watching. You have to watch To Aru Majutsu no Index also since both anime have some relation to each other only by different characters in the Academy City.
the comedy is hilarious & the fight scene is cool.