>>18217290well yeah they're not going into secret groups looking for people to exploit. That's /pol/s job.
But basically this group has already been well known. The gachikoi (being in love with an idol, actor, etc.; fan who is in love with an idol, actor, etc.)
All you have to do is be a popular Idol and say you love them being there and be somewhat personal with them. Thats why small idol groups actually do meet-ups post concert to try and gain a personal relationship with their group. Its an actual common strategy in Japan. Its just rushia turned it up several notches and made it from "Oh im glad you like my stuff :D" to "LOVE ME!!!!"