Ren's chosen "master" is Takeya, a Jerk with a Heart of Gold. This may seem odd, until it's revealed that as "the gate," her purpose is to judge if a species is a worthy source of the "love" that their species needs to live, and, to allow for a fair hearing, what better representative for humanity, as a whole, than someone who bears all the traits, both positive and negative, without going into any of the extremes.
Ren is ultimately revealed to be "the gate" whose ultimate purpose is to judge if a species can provide for the DearS' need to be loved. Any species that is found wanting is doomed to extinction, and Ren has no conscious control over this function. Even sending her off into space on a rocket is insufficient to avoid that fate. Now remember how she and Takeya met. He found her wandering on a highway, lost, confused, and with absolutely no understanding of the local language and customs. Why? Because her stasis container fell off a transport truck that was taking her to a laboratory where she was slated to be experimented on, as part of an official treaty where "defective" DearS are handed over for experimentation while the rest get human rights. Humanity could easily have been blasted into extinction without ever knowing why.
The fact that the governments of Earth see nothing wrong with demanding a sapient species handing over members of their population for experimentation in order for the rest of them to have citizenship rights is a chilling prospect in itself, however, the nature of those experiments is never fully elaborated, although a throwaway line indicates that it includes vivisection, and the DearS are almost completely indistinguishable from humans in terms of appearance.
The implications of Takeya being a little smarter and a little less scrupulous are chilling. Remember Ren has little to no internal moral compass and is eager to obey any and every order Takeya gives her. Considering the fact that Takeya is introduced being an Extreme Doormat, the things he could have ordered her to do are downright horrifying.