Pickers of Empty Cocoons is the seventeenth episode of the Mushishi anime series.
After receiving a torn and misaddressed letter, Ginko realizes it is time to replace the cocoon through which his mail is delivered.
Ginko meets Aya at an isolated house, where she is pushing rolled letters into empty silkworm cocoons, and testing various cocoons to send letters to her sister. She recognizes Ginko, and that it is about time his was replaced.
Through their discussion and flashbacks, it is revealed that mushishi use a mushi called uro to communicate with each other. Aya and her sister, Ito, were trained by an old man who could also see mushi, to spin double cocoons into two single-threaded ones, creating a link through which the uro mushi could travel, and thus deliver letters from one cocoon to the other. Aya and Ito were warned never to close any doors, because the uro would quickly multiply in enclosed spaces, and flee once the door was opened, dragging the human into their uro passageways, never to escape.
After having been apprenticed for several years, Ito, while napping next to the drying laundry, has a sheet blow over her. She awakens to see uro all around her. Aya finds her and removes the sheet, asking if Ito fell asleep, just as Ito tells her not to lift it. The sheet blows back, and Ito is gone.
Because of Aya's grief and use of mushishi letter carriers to find Ito, Ginko brings Aya to an open uro passageway, leading her in along a chain. Showing her the catacombs, he emphasizes that there are an infinite amount of places Ito could be, and urges her to stop grieving and seeking Ito out. After he leaves, it is shown that Aya continues to expect to see Ito emerge.
As the episode ends, the narrator continues on to tell that a silk crafter was shocked to find a girl inside the cocoon she was harvesting silk from. The girl could not speak, but with the help of a letter she was carrying, was delivered to her home village.