Brynhildr in the Darkness

As a child, Murakami had a close friendship with a girl he referred to as Kuroneko. Tragically, during an attempt to demonstrate the presence of extraterrestrials to Murakami, she perished in an accident that he narrowly escaped. Burdened by guilt over his involvement in the incident, Murakami resolves to spend his life proving the reality of aliens. Years later, a new student with enigmatic abilities joins his class, bearing a striking resemblance to Kuroneko and going by the name Kuroha, Neko.