This is my classification about vocal ranges of this girls. Contralto .- Shimizu Riko, Yamato Ao and Nemoto Nagi. Mezzosoprano .- Tsurumi Moe, Matoba Karin, Hiruta Airi, Kumamoto Marina and Okada Ayame. Soprano .- Kataoka Miyu, Yamamoto Rio, Yamasaki Nana and Nakamura Akari. Maybe I can be wrong but the greatest vocal range, almost 3 octave or plus are from: Nemoto Nagi, Kumamoto Marina, Hiruta Airi and Nakamura Akari. I think Yamato Ao could be a great singer in future years because her youth and energy. She has the louddest voice of them and an amazing physical condition.