A Certain Scientific Railgun Season 2 Episode 13

One way - Accelerator

Mikoto falls in despair, realising that with the Tree Diagram destroyed, she has no way of stopping the experiments. She tries to cling onto her cause by mercilessly destroying another facility, but loses all hope when she sees a feed of Misaka 10031 being killed by Accelerator. As Accelerator reminisces about his first experiment and his first time killing a Sister, Tōma discovers Misaka 10031's corpse and calls AntiSkill to investigate it, only to find it gone when they arrive, with no evidence it ever occurred. After the AntiSkill leaves, Misaka 10032 appears before Tōma, who comes to learn the true nature of the Sisters. Upon learning this, Tōma heads for the Tokiwadai dorms to try and get some answers from Mikoto, who at the same time is contemplating her last resort.