Omoi no Kakera - Close to Japan

Homura Motoki was walking down the street one day with his girlfriend Yuuna when they were struck by a car. When he woke up in the hospital, he realized something incredible had happened. He was having an out of body experience and no one seems to be able to see or hear him. Floating around in the air, Motoki set off to find Yuuna, only to discover she has lost all her memories of him because of the accident.