Talk:Toaru Kagaku no Accelerator Episode 01/@comment-3969505-20191001223511/@comment-205.237.215.217-20191001224742

It's an anime original to refresh the memories of people who might not have watched the show in a long time or newcomers who didn't watch it at all. I'm not sure why you're surprised, the first episode of Railgun is also mostly anime original. It's also not an unusual thing to do in anime adaptations, like with Fullmetal Alchemist Brotherhood's first episode.