Big Spider Arc

The Big Spider Arc is a minor story arc that occurs within the Toaru Kagaku no Railgun sidestory. It focuses on Big Spider, a faction of Skill-Out that has recently increased its attack on espers, and Konori Mii's involvement with them. This story arc is notable as it is the first arc made for the anime, however it is considered canon. This arc also introduces the first incarnation of Capacity Down, a device that does not appear until volume 19 on the Toaru Majutsu no Index light novels.