Hikaru's mad at Kirari because Kirari wanted Hikaru to apologize for saying Zakku-san(?) is ukki ukki like a monkey. But Hikaru insists it's ok because he's got headphones on and wouldn't have heard her say it. But Kirari says just because they can't hear you, that it's ok to say such rude things.
Maimai's such a punk acting as Hikaru, and Koharu was sooooooooooo cute when she got mad at the end of the episode XD