The robot companion of Agarta, 3-5-10 assists Agarta with her work & can communicate with her as she enters the clients consciousness. He is responsible for collecting the "payment" for the services rendered by Agarta as well as storing and organizing her memories. His other duties seem include running & maintaining her ship & communicating with clients. He makes a reference to the fact that he was once human.
Designed to be a general-purpose, if beautiful, tool for Kabapu, Ropponmatsu (Unit 1) excels in bomb-disposal. After failing in her first mission, she is given an additional form (Unit 2), that of a perky, young cat-girl. In the original manga, only one Ropponmatsu unit is active at any one time; the reason for this is later revealed to be that there is only one central "core" that is switched between the two bodies. Kabapu attests that the core contains the soul of the princess of the lost civilization of Solaria, and he has had the Ropponmatsu body created to house it as part of his plan to destroy all remaining traces of Solaria's technology. Conversely, the anime (produced before this revelation occurred in the manga), has the Ropponmatsus appearing as two distinct entities who frequently cooperate on important tasks. Although they have a tendency to be destroyed on their missions, Shiouji keeps a lot of spares, which play a large role in the penultimate episode of the series). The vast difference between the units leads to some tension between Kabapu and Shiouji: both incarnations of Ropponmatsu have a tendency to fail in the course of their duty, due either to extreme mass (Unit 1) or lack of appropriate functionality (Unit 2).
She is introduced in episode 3 as an assistant of sorts to the Female Informant from Episode 2. Much like her predecessor, she demands sex with either Rin or Mimi for information. Although, her first encounter with Mimi was less than romantic, by episode 4, they appear to have entered into some sort of relationship. After episode 4, she has apparently died.