When did Anna started to pay more attention to Kyoutarou?! I think it was around...

Hacker075 said:
I feel like it's more curiosity at first and then becomes interest (in the sense of already being comfortable with him but wanting to tease a bit and learn more) and then progresses more explicitly.

Onedux said:
Damn good post, i also wondered when she started to be interested in him, precisely because it was at the beginning that the romance between them developed in a very good way, props to them for creating a good romance between them that isn't too forced or anything real.

Playcool said:
Starting when she was hit with the basketball, she was staring at him.
I was wondering when such a thing happened, while seeing S1 and even after finishing S2, but now that I got to read the manga, I found this extra: (Chapter 119.1 Twitter extras)

http://imgur.com/a/b4Qkw1m.jpg
(kinda wanted to show it directly, but [I"mg]link[/"img] is NOT working for me somehow, I inserted " " on purpose, to show the code)

According to that, it was during October, which must be after the basketball incident, because starting episode 4 of S1 when she hears the blazer (and the cardigan), then she is already interested in him, even asking him to let her ride his bike.
But it actually makes more sense if it was when she was hit with the ball in the nose, that was the moment she was like really getting really interested in him.

I was under the assumption she liked him since the start of the series, but that is not true, she just liked to eat snacks, thus found the library and from them started to interact with him more, and since she is an easygoing person was just chilling around until she starts to pay attention to his actions (episode 1 ending was the trigger when she started to find him funny and a bit interesting).

When the like started, it seems harder to say, by the end of ep6 of S1, she was definitely into him, so it feels like it was between ep5-6 of S1, subtly.

Also, you must say, why are you using the anime as a reference? Well, I have yet to read the start of the manga, and will do so when I catch up to the release of the manga, until then I only have the anime reference, and this picture was from the manga too, so found it better to do here, while asking for other opinions, to check my theory is right or not.