Furin maruhi kôkai: Hitozuma-tachi no nureba (1997)

One day, Kayoko, who lives near the Tama River, picked up a strange bottle in a park along the river. She might have come down the river. Her interest was piqued, and she pulled out a piece of paper inside, where she wrote, "Please contact me, who is living a lonely life underground." She asked me to put the replies in this jar and keep them in the same place. Kayoko thinks she's playing a prank, but just for fun she takes the bottle back to her house, where she writes a simple reply and she returns it to the same spot in the park the next day.