I'm calling it now. This 'sister' is actually a brother - their family has a daughter that looks like a boy and a son that looks like a girl.
Wah! Naru! How long have you been there!?Ffufu!I ain't telling you nothing, stupid!Tell me all about it later, okay?Get out! I'm changing!The hell you talking about?Gross, dude.It's making me all excited.Hearing Mizuki using such sweet voice.Fufufu.How long indeed.Your boyfriend?Who was that on the phone?