All this author needed to do was deliver Yukiko fanservice every chapter, the first chapters were literally full of it, that was the hook, because he obviously doesn't know how to write. And why sell it as a romance when it isn't one.
Naoya could film himself having a threesome and Mirika still wouldn't stop. Time to accept his role as the harem master. Looking foward to the fanservice next chapter.
Mirika got pretty agressive, this is becoming even more interesting. It's a good thing she's not joining as the third girlfriend but as a legit love rival to the other two.