I think the big problem is in these kinda mangas the FMC and the MC are always destined to end up together at the end.
But this time the author realised along the way that Hayami is the better girl and I bet that Hayami is also more popular among the fanbase.
So he never had the balls to write...
Man this started of pretty good. But somewhere after adding the 2nd girl and before adding the 3rd girl it becomes complete trash.
The girls all magically fall for him on first sight. All of a sudden they have more and more complex technology but only him.
Spare yourself the time and just dont...