Anna is an idol. She hasnt been famous yet, but we already have a glimpse about what her fan would do if she got a bf. Manager-san also warned ichikawa about this.
She isn't an idol, she's just a model. There's a difference. An idol performs on a stage in front of live audiences, singing and dancing. Anna has no aspirations to this effect, and has currently only wanted to be what she has been so far: a fashion model and actress.
She's still a form of celebrity, though, because of that, which does mean there's risks. It's just it'd be a lot worse if she really was an idol, where restrictions on dating really are more of a thing than otherwise. As an actress and model, she's not as expected to stay 'chaste' as the far more otaku-oriented idol profession. But it's still a concern as far as Anna's potential futures and possible acts of rabid fans.
At the same time, she's not all that big right now, and there might be value in making it clear she's in a committed relationship early so it's part of her celebrity identity going forward.
Still, we have to get to the stage where that's a comfortable thing to declare, if it is even to be declared.
Either way, having them consider each other as dating is still a major step, and they still both need to be ready to think of each other like that.
But it is coming, we're in the home stretch on that.
... anyway, now that I've yammered about that topic...
Yurine is so damn cute.
I love the little things, like Anna swooning over the line that'd probably be fitting for Nigorikawa (male lead from Your Color's Octave, the shoujo manga Anna introduced Kyo to), the 'sorry' in the book, Yurine trying to be helpful, but arguably making more stress in the moment...
The whole note in Yurine's book thing was great, and Kyo acknowledging certain things as precious for both of them because of it, but also stopping himself before he went too far, because he really shouldn't be reading that note, but it still gives him some needed pushes, all the same.