I swear, most of the girls in this manga don't seem to have a working libido.
Adolescence is a time of bursting sexuality and raging hormones. The brains of these girls should be going overdrive with sensual urges. And yet, most of them show zero sexual reaction to physical stimuli: even when they are alone in the house with their love interest and have just shared a kiss on the mouth, they don't seem to be aware of what comes next.
Some are exceptions. There's Nao, the pervy one, and then Mio and Shizuka; they're the biggest exceptions. Kaoru, big vamp that she is, must have a sexual interest in all those girls she seduces. And Mari actually has had onscreen orgasms, helped by Yuu... who strangely never seems to be turned on by the sadistic things she does (she does enjoy herself, yes, but it appears to be purely cerebral).
And what about the others?
Everyone else's hormones seem to be out of commission. [¬_¬]
I think I'm probably going to piss some people off with this, and sorry if I come off as kind of wet-blanket-y, but...They aren't love interests? I mean, not officially, for the most part. Ai and Chie clearly think of themselves as a couple, and there's MIo and Shizuka, and maaaaybe Mari and Yuu? Although they've never really put it in words, so they might still be skating on plausible deniability. Most of the others are, officially, just friends who are skirting the line.
There's a thing that allegedly happens in girl's schools where girls "play at love" with other girls, which is to say they entertain homoromantic relationships but internally many of them expect it to end when high school does. Most yuri manga treats this as an obstacle to the "main couple", (see "Run Away with Me, Girl" for a prime example) but for a series like this, that doesn't focus on a single pairing that much, It kinda ends up feeling like a sword of Damocles over the entire series.
Not saying many of these pairings don't "mean it", but a lot of them seem to be holding back on committing to something they don't expect to last. Generally, high school relationships don't last past college anyway, but I expect gay relationships coming out of a girl's school have a particularly bad batting average. That doesn't mean things are gonna go bad here for any or all of the pairings, it just depends on the kind of story the author wants to tell. (I expect the series will just end with everybody still in high school so the readers can imagine whatever ending they want for their favorite ships) But it does kind of inform the expectations the characters themselves might have.