>bond up Dress Saori absentmindedly
>says, basically, "Something feels tight in my chest...I'm not sure what's going on. Do you know, Sensei?"
Oh
huh

So this alt is where she starts falling for you, eh? Default Saori doesn't have any such lines, "Swimsuit" Saori only has like "I'd like to perform for you". Looking into it, Dress Saori has at least 2 lines indicating she's started catching feelings (the other apparently is one where she says she'd like to wear her dress specifically for you)