This series is character of the week with a loosely connected plot and minor Nanako subplot so harem ending was the best way for it to end. It could have been better with interactions between other girls in the club but it was never structured that way.
My headcanon is that the other girls do have sex with each other, but that they won't if they get together with Miyako.
That's an awfully big harem though. I hope Miyako stays in shape!
In my view this is a story about two girls who are madly in love with each other but can't show it in a normal way to save their lives. Komaki especially should buy a clue or two.
やっぱり in Japanese is something said when you get confirmation of something. So it's usually translated as "I knew it", "As expected", "Sure enough" etc.
It's a bit weird to translate "yappari" as "Just as expected."
I also think Mitsuki may be a tad young to take on the responsibility of a shop owner, aside from all the legal stuff that would have to happen first.
What is it with Japanese rockers and the Red Hot Chili Peppers? If these girls are math rockers they should be listening to Polvo or Slint or something.