The third arc of A Certain Magical Index, consisting of volume 3 of the light novels, chapters 11-21 of the manga, and episodes 10-14 of the anime.
An extended interpretation of this arc from Mikoto's viewpoint can be found in the A Certain Scientific Railgun manga, and was episodes 2-16 in the second Railgun anime.
- Clones Are People, Too: The sisters start off placing zero weight on their lives, but by the end, Touma convinces them that they're still each unique, and they start treating themselves as people more.
- Hive Mind: This is the arc where we meet the Sisters Network, a network of 9,969 (remaining) clones of Mikoto Misaka, using their level 2 Electromaster powers to remain in constant contact with each other.
- Power Levels: Accelerator is a level 5, like Mikoto, but he is far more powerful than her, and is easily the most powerful esper in Academy City. The clones, on the other hand, each have 1/20,000th of Mikoto's power, and are ranked at level 2. Despite Touma's ability, he is ranked a level 0.
- Reality Warper: This is the arc where Komoe explains more of how esper powers work. Specifically, they each have a "Personal Reality" they impress on the world, which allows them to make minor alterations. More powerful espers are ones with a stronger belief in their Personal Reality, and thus have a larger effect on the world.
