I know I said I wasn't going to read this anymore... but I have to know what happens. And as for people saying Kotooka is selfish and dramatic and stuff: well, I'm okay with that. She's only like, what, 13? Lots of girls get their periods around that age and speaking from experience, that can be some mood fucking shit, not to mention just being an adolescent on top of it.
As for her selfishness over Tsukasa--Kotooka is a girl who went out of her way to learn Tsukasa's favorite foods, learn her interests, and even got her what she wanted for her birthday. She may go about things poorly at times, but this girl puts in a lot of effort to try to make her beloved happy. I know I'd feel lucky to have Kotooka as a girlfriend.