After Kazusa reads about masturbation at the bookstore (no doubt learning it’s natural and healthy and thus way less of a big deal than either she or Izumi are making it out to be, even if it was super-embarrassing) she finds Niina in the clutches of some mouth-breather, and gets a text asking her to follow, along with other instructions.
When Kazusa joins them at the cafe, Niina is acting like “a different person”, talking about having to “take on three guys at once” later, then asking the dude if he’d hook up with her “super slutty friend” instead. That’s when Kazusa declares, loudly and proudly, that her crotch is really itchy. The guy flees.
Turns out it was all according to a script Niina’s friend at a theater troupe gave her to use as a defense against the many guys of all types who have projected their fantasies on her due to her ethereal, girlish good looks, and in doing so push past normal social boundaries. It’s a sad but very accurate commentary on the need to know how to deal with such men; many of whom won’t take rejection well.
Because of her looks, Niina grew up a little faster than the other girls. As for Kazusa, she really only grew up when she walked in on Izumi, who her clueless dad invites over for pizza. Izumi
and Kazusa have a mature and productive chat about it briefly tries to make Kazusa forget by grabbing her head and shaking it (the childhood friend rambunctiousness coming out at the worst time) but ultimately would prefer if she just forgot it ever happened.
Later that night, in the shower, Kasuza puts herself in Izumi’s shoes, and of all the things she’d want to cover if he walked in on her, she determines she’d probably most want to hide her face, as if like an ostrich with its head in the ground, it wouldn’t be happening if she couldn’t see it.
At lit club, Rika instructs each member to come up with ten more “literary” words to use in place of the inartful English word “sex”, since it’s an otherwise unavoidable word with the works they’re reading. Then the writer among them gets a call from a potential editor, telling her she’s not quite there yet, but coming by his place will “probably help her chances.”
Then Rika gets “bothered by the chidings of lascivious beasts,” causing her to hurt her crotchal area on the vault; one of the girls doesn’t laugh and wonders out loud if she just “broke her hymen”; Rika later admits to herself she “doesn’t know how to check”.
It’s just and overall unpleasant-as-hell experience, but as she’s washing her face in the sink, Amagi comes by and calls her cute again, even comparing her to a model. There’s no reason to think the kid is messing with her, but Amagi isn’t prepared for the praise, and flees in a cloud of dust.
Then, the inevitable: the girl who boasted to her friend she’d take Izumi’s virginity makes her move. Kazusa is instinctively ready to riot, even tossing out the lame excuse of “having to keep an eye on him while his mother is busy with work!” She ends up getting to watch the meeting thanks to Niina paying her back for “having an STD for her” the other day.
Izumi ends up turning Asada down, but when she learns he doesn’t like anyone in particular, gets him to agree to “think about it,” as she’ll wait for him “forever.”
After Asada leaves, Izumi spots Niina snooping and recording, but Kasuza comes between them and tells the truth: Yes, they were snooping, but he didn’t give the girl a straight “no.” Then she asks if he just wants to “do it” with girls, and Izumi doesn’t understand, she blurts out a variant of one of the club’s euphemisms: “Ess Eee Ecks!” before running off.
The next day, with the whiteboard full of vulgar words and phrases, the principal and vice principal, both men, declare that absent a faculty advisor to keep them in line, the lit club will be dissolved. Kasuza starts weeping form the news; she doesn’t know what she’ll do if there’s no lit club (answer: they can always meet up somewhere after school and in the summer).
But Niina knows better. She knows Kasuza’s tears that just won’t stop aren’t just about the threat of the club dissolving. She gets Kasuza to admit that a “storm is raging in her heart”, and that if she absolutely had to “do it” with someone, it would be Izumi, which indicates she likes him. This may be something we’ve known for a while now, but only then, on the riverbank, does she finally have the official epiphany. She’s in luuuuuuve.