The Retrieval Unit (忘れるもの係) consists of 5 members. They were handed to the Three Professors after Dr.Coppelius was chased out of his lab. They are forced to follow whatever the three scientists told them to do, because every member of this unit had a chip implanted in their head and will set off at a push of a button (Dr.Coppelius later resets this and set them free). Right now they are sent by the Yellow Cake company to secure Aoi . Members of this unit had worked at SITE-0. They mainly contact through channel 4.
After the assault in Tokyo Station, the Retrieval Unit ended up disbanding. Yet, it is shown that in the end of Chapter 221, Setsuna reappeared and seemed to regroup the Retrieval Unit into one once more, excluding Kiara.