The Walker Droids are used for cleaning the city. Every droid has its own identification chip which allows it to pass through every check point, in order to clean the area.
Appearance[]
Plot[]
Sampo is the first walker droid seen in the anime. It is first seen cleaning trash around the park. In episode 2, Nezumi uses Sampo to block the path of a police car to help Sion escape.
Difference in Anime and Manga[]
In the Anime, The Walker Droids resemble different animals like elephants or penguins, while in the manga they look like regular robots.