Volume two ends on a cliffhanger with possible progression into NTR due to female MC (Arisu), separating from male MC and follows the main antagonist which just so happens to be her brother. However, with prior knowledge of following volumes, the female MC stays true to the male MC and gets rescued during a critical moment, male MC then goes on to kill her brother. This twist also allows male MC to develop physical relationship with other members of the party to establish the harem.
The fact that the author hints and sets up romantic interests around the protagonist but doesn't progress with it at all, seemingly scared of breaking the balance and putting off readers who support either female protagonist is disappointing and frustrating over time. The way the plot progresses makes the reader wonder whether the events in previous volumes even transpired, as though the relationship between characters just simply reset themselves when they should have grown much closer over all this time spent together.
The only noticeable progression we see is between the male sub-lead and his romantic interest over the course of one of the earlier volumes. The fact that the author pairs up the two male leads all the time creates an endlessly stoic environment for mindlessly increasing the number of volumes/books sold, exploring problems surrounding modern day society with insight no more than that of a typical high-school student.
Essentially, to summarize, if the author took the plunge and either progressed character relationships or even wrapped up the series earlier, would have earned a much higher evaluation as a whole in différance to other similar works.