So... is Gokukoku no Brynhildr finished or not?
NO, it is not finished.
Why?
The anime finished before the manga:
Anime finished: June 29, 2014
Manga finished: March 31, 2016
MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
Here you have all the anime relations we detected ordered by release date, so you can see the reason for this status in context and also use it as watching order.
The mangas and the non-core contents are excluded by default, but you can enable them by clicking the buttons below:
Synopsis
Ryouta Murakami, driven by a childhood tragedy involving his friend Kuroneko and a quest for extraterrestrial proof, is now a high school student still determined to find aliens.
His life takes a dramatic turn when a mysterious transfer student, Neko Kuroha, appears, bearing an uncanny resemblance to his deceased friend and exhibiting extraordinary powers.
As Ryouta gets closer to Neko, he discovers a hidden world of escaped witches being hunted by shadowy scientists.
Now, Ryouta finds himself compelled to protect Neko and other witches like her, caught in a dangerous game between science and the supernatural.