I don't really see the problem here? Well, except for the incest bit, but I don't really think it's pedophilia. The average age in starting junior high school in Japan is 14-15 (same thing here in the Philippines), and Rentarou being only 2-3 years apart assuming she's 14.
It isn't really THAT big of a gap compared to Hahari's age.
And speaking of Hahari, we finally have an adult parent character that ISN'T a girlfriend or just mentioned briefly in, like, one page of the manga. Finally, some more world development.
Hope we see more characters soon that are outside the GFs. I dunno, maybe some guys being jealous at Rentarou for being popular, or people spreading bad rumors about him being a playboy who lays his hands on women; something like that.