[Update] The teaser video has been removed from YouTube.
For those who don’t know, Railgun is a spinoff of Toaru Majutsu no Index, which set in a world of magic and superhuman powers.
Railgun focuses on the “scientific” side with Mikoto Misaka, a powerful electromaster in Academy City, as the protagonist, in which she fights off crazy people (and enjoying her everyday high school life) together with her friends and love interest.