There are many different kinds of lives in this world When everyone is gone only the afterimage remainsAi 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