Kakyoin, Jotaro and Eileen discussion coming your way 😉
I'm under the impression that Kakyoin had just transferred to Jotaro's school pre-SDC since Jotaro's fangirls didn't recognize him (although that could also be their Jotaro-focus making them not really care until interaction).
I'm also going to suggest that Kakyoin (mind-controlled at the time) suggested the transfer himself ((using a different reason w/his parents like: Jot's school has a better reputation/whatever). He knew which school because when Dio sent Kakyoin after Jotaro, Dio was able to determine Jotaro's location.
It's kinda funny.
Now, how does this relate to Eileen (cause God knows I don't have to explain why I mentioned Jot in my premise)?
Eileen was kicked out of her previous school a couple of months pre-SDC, so she actually has a vague awareness of Jot before the series picks up again.
It's hard not to notice the guy who has a whole crowd of girls flocking to him?
She's kinda perplexed: how did this happen, why do these girls keep coming back, oh my god can I get some peace?
I don't think Eileen is particularly sociable after her face-scarring. No one really wants to hang out with her, she's got big scars on her face, rumoured to be kicked out for fighting (true...), and doesn't talk to anyone. So she doesn't exactly have anyone to ask these questions to.
Of course, all the while Jotaro's got his own pre-occupations. Attempt to cope with the sensory overload his fangirls are so talented at providing. Worry about this new 'evil' spirit which makes the fights he already gets into even more violent (it's as if it's feeding off his anger...?). Do at least some school work. Etc, etc.
Of course, then SDC happens and these three people, whose lives wouldn't have crossed if it weren't for these circumstances are thrown in really close quarters.
They have to talk about SOMETHING.
Kakyoin has to have some sort of inkling of curiosity about his friends' lives pre-the-DIO-ning and Eileen actually has the opportunity to ask what the hell was with Jotaro's fangirls!
It turns out that at first it was one or two girls that were into Jot. He wasn't really picking up what they were putting down exactly (tbh they weren't forthcoming) so he was just polite. The girls felt emboldened by the lack of negative reaction and began pushing more stuff: "what do you think of this? Can I do that?" Calling him Jojo.
Now it was an inconvenience. Jotaro rejects them, but they don't really take no for an answer. It slowly becomes more and more girls, (each one of them thinks they're going to be 'the one' to 'break his aloof mask' and that these other girls are wasting their time/jealous/etc.) They begin fighting amongst themselves while pursuing Jotaro's attention.
This is around the time that he starts swearing at them, trying to get them to Fuck Off, because being nice Clearly wasn't enough.
(I think This group that follows him, kinda just built up fantasies in their minds of who Jotaro is, what they wanted. And he was handsome and didn't say much so they could have their impressions.)
I don't think Jotaro really cares about the why or the how, to him, he was a nice classmate, and the next thing he knew he was being overwhelmed with all this damn attention. That's what he tells Kakyoin and Eileen. They thought he was hot, he guesses, and they wanted him to be theirs.
"It's so damn exhausting. I'm almost glad that..." he paused. "The quiet is nice."