Jyu Oh Sei, No.6 Recommendations
Both have sci-fi and a sort of futuristic feeling. Both involve as main protagonists, a lively girl who loves the main protagonist (a white haired boy) and that boy makes a sort of "best friend" where they are always together, and the three of them try to find out the truth behind the mysteries involving their home planet/city.
Both are about surviving in an unforgiving world after being cast out by society, Jyu-oh-sei to Chimera, a planet where plants are the biggest predator around and No.6 into the wastlelands where everyman fends for himself.
These similar themes could apeal to the same people i believe even though the plots and characters are pretty different, but for those who likes Nezumi more than anyone else in No.6 i think Jyu-Oh-Sei will prove a good series, though you have to tough out the first two episodes before you get hooked!
They are also both animated by the studio Bones.
The two are very similar in the way that there is a governmental force or a force of a higher individual trying to manipulate or take over. There is conspiracy theory in both and there is a certain level of action. Both of the main characters have people that become fond of them and help them in some manner.