Usually the jokes are about calling the police because of a little girl, but this is about a little girl calling the police about a guy and an older woman. So I guess the boy is the "loli" in this situation? (Underaged, I mean, if only just barely)
author: "dang, I need some way to make the development go even slower"
editor: "You need to introduce a loli in this!!"
author: "THAT'S FUCKING IT!!" (☞゚ヮ゚)☞
All things considered, this is a pretty good way to prevent development. Realistically, he should get used to Onee-san's personality eventually and then just fuck her brains out. Now the story has an "alibi" for him not doing it.