The second season will focus on The Sisters Arc. Lasting only a single volume in the Toaru Majutsu no Index light novels, it was later expanded greatly in the Toaru Kagaku no Railgun manga. The arc focuses on the ordeals of Mikoto Misaka after discovering the existence of the Radio Noise sisters that are being used in the Level 6 Shift, an experiment where they are killed in order for the highest-ranking Level 5, Accelerator, to achieve Level 6.
I watched this like a month ago, but I forgot to write about it (mostly because I was lazy as always..^^''). I really liked the first season of Toaru kagaku no railgun so of course I watched this too! This was good, but not good as season 1 though. The start was really good when the sisters was the main thing.. but then 17-24 episodes.. I didn't like that part so much for some reason :/.
BUT this was really interesting and cool~