Well, Ayaka, Kanon, and Yuuka are the voices of the characters in the anime called Lilpri. They also sing songs for the anime too (like the videos you showed me). There are three main characters in the anime. The characters are Yukimori ringo who is played by Wada Ayaka (pink girl), Takashiro Reira(leila) who is played by Maeda Yuuka(blue girl), and Sasahara Natsuki who is played by Fukuda Kanon(purple girl). Saki is currently an Oha Girl, its for a television show primarily but they also have a song and music video. If you search Oha Girl or Oha Girl Maple, you'll see her there. Oha Girl Maple is kind of related to Lilpri.