Getting an interference from a similar power to hers, and being guided by her intuition, Mikoto comes across a girl wearing a Tokiwadai Middle School uniform. Like looking into a mirror, the girl looks exactly like Mikoto. While the two stand in silence, the girl utters a single, strange word. The girl calls herself “Misaka.” Mikoto, fully grasping the girl’s relaxed pace, helps the girl save a cat who is stuck in a tree. Afterword, Misaka calls Mikoto “Onee-sama,” which easily affirms the fact that she is a clone. Mikoto is completely bewildered by the perplexing turn of events.
(from the official episode guide)
Mikoto finally meets her clone. However, for some reason, the clone seems to move at her own very slow pace. Mikoto spends the rest of the day following her around hoping the clone will lead her to those responsible. After night falls and realizing the clone will offer her no help, Mikoto says goodbye, but not before giving the clone the Gekota badge she won earlier that day. While searching for the purpose of the clone’s existence, Mikoto learns the cruel truth.
Grasping the gravity of the situation, Mikoto rushes back to find Mikasa. What she finds is a horrific scene and a snickering esper standing over Mikasa’s dismembered corpse. Witnessing the tragic moment with her own eyes, Mikoto goes into a rage and rushes to face off against this mysterious esper.
TV Anime A Certain Scientific Railgun S Official Site:
http://www.project-railgun.net/ (Japanese)



