Toaru Kagaku no Railgun: Cold Game (とある科学の超電磁砲 コールドゲーム Toaru Kagaku no Rērugan Kōrudogēmu?) is a short light novel released on December 27th 2017, celebrating the manga's 10th anniversary. It is later included in Toaru Majutsu no Index: Gaiten Shoku Light Novel Volume 02 alongside the compilations of Toaru Kagaku no Railgun SS: Liberal Arts City and Toaru Kagaku no Railgun SS2: Shopping Mall Demonstration.
During a Social Studies field trip to the Central Anti-Skill Station, Saten Ruiko discovers that a person in the background of one of the photos on her smartphone is a criminal on the wanted list. As a result, Saten, Uiharu, Mikoto and Kuroko find themselves involved in the Cold Sleep Murder Case.
- Alfonso Brookman (referenced-only)
- Asajimo Saemi
- Asajimo Mebuki
- Innai Chigiri
- Puppy Prosecutor
- Tsujinaka Kyouka
- Matsuoka Raita
- Electromaster (Railgun-variant) - Misaka Mikoto, Level 5
- Teleport - Shirai Kuroko, Level 4
- Ion Trade - Matsuoka Raita, Level ?
- Academy City
- The parts of the story are designated after the Tarot's Major Arcana, in numerical order.
- The story shows glimpses of how Academy City has not only a constitution but also the inner workings of its judicial system.