Though Accelerator may be recovering from his injury, the dark side of Academy City never rests, and so he finds himself unwillingly caught up in the midst of a new conflict. When a mysterious young woman approaches Accelerator in pursuit of Last Order, the highest-ranked esper is confronted by a venomous organization that has taken root in Anti-Skill, Academy City's peacekeeping organization. With dangerous forces on the move that threaten to put Last Order and her sisters at risk, the self-proclaimed villain prepares to step into the darkness once again.
English: A Certain Scientific Accelerator
Synonyms: To Aru Majutsu no Index Gaiden, Toaru Kagaku no Ippou Tsuukou
Status: Finished Airing
Aired: Jul 12, 2019 to Sep 27, 2019
Season: Summer 2019
Studio: J.C.Staff A.C.G.T.
Duration: 23 minutes