Boku to Iu Mono

The protagonist character has 'lived' alone and unfeeling as a conscience inhabiting random objects and animals for random times for as long as he can remember — but one day, he turns into the shape of a human boy. His life changes utterly when the human girl Sae decides to try to befriend him, naming him "Ao" for his deep blue eyes as he cannot speak. Every day, they have fun playing hide and seek — but one day, Sae stops coming...