There are many different kinds of lives in this world. When everyone is gone only the afterimage remains.Ai has only recently came to Tokyo. In this unfamiliar city she is a little bit upset. One day lead by a mysterious stray dog she finds a letter inside a hole in the tree trunk. Tomohiro who works night hours at a nursery hadleft it there. Ai being encouraged by this letter writes a letter back and leaves it in the hole. This was the beginning of their strange correspondence.