"Sisters" (妹達(シスターズ) Shisutāzu?, lit. "Little Sisters") is the 4th episode of the Toaru Kagaku no Railgun S anime series, and the 28th episode of the anime series adaptation of the Toaru Kagaku no Railgun manga series. It was first broadcast on May 03, 2013. The episode's script was written by Sunayama Kurasumi, storyboarded by Muroi Yasuo, and directed Sakurabi Katsushi. Behind the scenes of the vast landscape of Academy City, a certain experiment was in progress quietly.