とある科学の超電磁砲外伝 アストラル・バディ ; とある科学の超電磁砲(レールガン)外伝 アストラル・バディ (Japanese); A Certain Scientific Railgun Side Story: Astral Body (English); Toaru Kagaku no Choudenjihou Gaiden: Astral Body
The manga focuses on a certain unnamed character who appears throughout the story of A Certain Scientific Railgun and A Certain Magical Index, and whose name is revealed in this story set at Tokiwadai Middle School.