I'm thinking the qualifications were 1) bilingual and 2) some sort of celebrity status. Of the 10 girls, the eight Japanese seem typical "groupthink" Japanese, they don't try to stick out and they mostly include other girls in their pics and vids. Natalie, the blond, is much more brash and likes attention (typical Youtuber) and Megumi, the half-black girl is a self-promoter.
https://video.twimg....UMlgxWafol_.mp4
I think I was wondering because Natalie is an American girl who had only been living in Tokyo for 3 years
I assume the others have some sort of Japanese background. Like Wakayama, she is Australian but she is of Japanese descent.