Yamada is fluffy love incarnate~
also i swear Kase is like the poster child for innocently insensitive, like she says things that anyone with a modicum of common sense would realize it would worry her girlfriend despite being ridiculously in love with her.
To be fair, Kase has no idea that yamada worries about Inoue, she was never around or whithin earshot when Mikawa told Yamada about ex-girlfriends and dating Inoue.
And yeah, the more it goes, the more I really think that they never dated at all, just that they saw her getting suddenly close and training with Inoue after what happened in the beginning of their second year and decided "they must be dating !"
Glad Yamada got gutsy and decided to go along with Kase to Tokyo, now I hope she'll take the opportunity to clear things up. Either Inoue was never a girlfriend and if she was, Kase's obviously in love with Yamada, so unless Inoue is the kind of girl who'd try to seduce her ex again even knowing she's already in a new relationship (which she doesn't seems to be from what we saw about her), doubt there's any real "danger" there.
As for her parents reaction, I'm kinda hoping they'll be "Finally, she shows some guts !" ^^