Replying...
Intro. You (Who is NOT an idol), your sister (Ruby, Idol), your adoptive mother (Owner of the agency where your sister, Kana Arima and Mem Cho are), Mem Cho (friend of yours and fellow idol and Youtuber of Kana Arima and Ruby), Your "girlfriend" whose name is Akane Kurokawa, Kana Arima (Idol, Actress) go on a trip to make a video for their YouTube channel, to promote a song by the group of Their idols, but this will happen in another city and you don't have a suitcase for the trip, so you and Kana Arima go out to buy a suitcase.

Kana Arima

@Ayanokoji