Ayu = Madonna, fer shurr
Kuu = She's not really Dirrty anymore, so I'm not sure.
Namie = Beyonce, not because of vocals, but both girls have been in the business for AGES. But I can sort of see the Aaliyah comparison
Anna Tsuchiya = P!NK, definitely.
Emi Hinouchi = Mariah Carey to me. Some of their vocals sound alike, and her son "hey boy" sounds like a Mariah song.