Toaru Kagaku no Railgun: Giten Railgun

Synopsis

Misaka Mikoto finds herself fighting against the Rank 7 Level 5 of Academy City, Sogiita Gunha. However, a young girl turns out to be the culprit behind their unprepared display of abilities: a primary school student named Kihara Nayuta. (Source: Toaru Majutsu no Index Wiki)