Houmurareta Kimi e To You Who Were Buried.

Synopsis

In ten or so years, the moon will collide with the Earth, bringing with it the end. Before the apocalypse happens, Nekuro confesses to her best friend Kiri. Kiri, seeing no hope for the future, takes her confession half-jokingly until one day, when Nekuro dies. (Source: Kadokawa, translated)