This... really goes quite painfully out of it's way to create fetish situations, without really paying any attention to why it's doing it; there's neither heart nor brain behind it. The protagonist gets in ecchi situations regardless of which girl he's in the room with, and the pretext for what's going on don't even try to make sense half the time...
Well, I don't know why I'm even bothering to complain; it's just mindless fanservice through-and-through, which is nothing new.
I guess I was sort of more hoping for some sort of silly self-indulgent romance beyond the ecchi. Instead of, like, "oh, let's introduce another girl for a different kink angle," which is apparently the level this is operating at.