These are character concept arts used for the anime.
Gokukoku No Brynhildr Character Concepts/Designs[]
Nanami concept art.
Ryouta Murakami concept art
Kotori Takatori concept art.
Kuroha Neko concept art.
Kana Tachibana concept art.
Kazumi Schlierenzauer character concept art.
Mako Fujisaki character concept art.