Inai Boku wa Hotarumachi ni Iru

Despondent over the death of his best friend, Takeru wishes on a shooting star to meet Takuya one last time. A glimmer of light leads him to an ancient tree stump with a giant hole in it; a hole that impossibly leads to an entire city. It's the same city as his—the same people and places—but, with a key difference: the Takuya in that world is alive and well...while Takeru is not.

(Source: Lovely Strange Dark)