Ayaka Nishiwaki (西脇 綾香, Nishiwaki Ayaka), nicknamed A~chan (あ～ちゃん, stylized as a-chan), is a Japanese singer and dancer. She is known as one of the members of the Japanese electropop group Perfume. Ayaka Nishiwaki (西脇 綾香, Nishiwaki Ayaka), nicknamed A~chan (あ～ちゃん, stylized as a-chan), is a Japanese singer and dancer. She is known as one of the members of the Japanese electropop group Perfume.