Close to: Inori no Oka

Homura Motoki and his girlfriend Yuuna are struck by a car. Motoki wakes up in the hospital in a state he does not immediately understand: he is having an out-of-body experience, invisible and inaudible to everyone around him. When he finds Yuuna, he discovers that the accident has erased every memory she had of him — she does not know who he is. Motoki's body is alive but can only be sustained for a few more days. The only way to return to it is to make Yuuna remember him before the window closes.