Inasmuch as she has the best overall aesthetic among the five; I can't shake off the feeling that she, out of all the characters, is the least best girl.
It is rather difficult to give a clear preference, because each one of them has interesting from my point of view, but I would probably say Nino, sometimes I would like to be so straightforward (I want to emphasize that I don't narcotize my boyfriend!) and I like her caring side.
Eh, yes, I'm trying to learn some Japanese and yes, I know what that word means ... eh eh, it has various meanings ... let's say ... a kind of "feeling" ....