The story is sort of about some country kids who have moved from Tokyo and are experiencing culture shock with their new environment as most people will, especially at a very young age like these girls are. It's a feel-good series that will brighten your days even if your sad with rare touching moments in it. Not a very original plot with cliched characters.
I don't know why people are so into these characters, they're pretty much your typical whiny kid. The only one I like out of the bunch and is my favorite character is Natsumi, now she was fun to watch but not great because she does get explosive. But the other characters are mediocre, Hotaru is a crybaby, Komari is a know-it-all who hates being called and treated like a little girl. And the youngest girl (I forgot her name but I think it's Rin), rather acts more like an adult than a kid.
I'm one who doesn't think this needs a sequel because I'm not fond of Non Non Biyori, it was a childish and silly comedy series with some weird elements to it, not surprising for a series aimed at kids but even they might find some of the series' music too babyish. Though, the series is not very very weird but it's still weird. Though, some parts did make me laugh but some jokes fell flat.