Although this is another spin-off of a certain dark-side group, you're entirely to blame if you complain about the episode not properly introducing the characters. So, it's better to watch or, better yet, read the Toaru novels. This anime takes place one year before the first episode of Toaru Majutsu no Index or in the light novel timeline, one year before the events of the first volume of the Old Testament. My first impression? I genuinely haven't read the light novel source, so I can't offer the perspective of someone who has. I was even surprised to learn that the source material is a light novel, unlike with Railgun. However, it was an entertaining first episode with an adequate amount of action and fan service. There were also some appearances that were essentially a treat for light novel readers, particularly those who have read the New Testament of Index. So, that was nice 👍