Toaru Majutsu no Index Gaiden: Toaru Kagaku no Dark Matter  

Toaru Kagaku no Migen Busshitsu, A Certain Scientific Dark Matter, とある魔術の禁書目録〈インデックス〉外伝 とある科学の未元物質〈ダークマター〉

A spin-off of Toaru Majutsu no Index focusing on the past of Teitoku Kakine.