Brynhildr in the Darkness

When he was a child, Murakami was infatuated with a girl he called Kuroneko. She insisted on knowing about aliens and having met them, but no one believed her, even young Murakami was skeptical. One day, she decides to show him the aliens, but an accident occurs and Kuroneko dies while Murakami is left seriously wounded in the hospital.

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