The story is set in a world where supernatural powers exist through science, and magic exists through religion. Academy City is home to 2.3 million inhabitants, which include ordinary civilians and ESPers: individuals with special abilities. 80% of the students in Academy City are active in the "Power Curriculum Program", and out of that 80%, only 7 are classified as Level 5 ESPers. Meet Level 5 "Electromaster" Misaka Mikoto and her friend Shirai Kuroko, who both work together in maintaining peace within Academy City's university district as members of "Judgment", Academy City's student-based disciplinary committee. "Toaru Kagaku no Railgun" ("A Certain Scientific Railgun") is a side story of "Toaru Majutsu no Index" ("A Certain Magical Index").