A~chan (あ～ちゃん) is a member of electropop unit Perfume. A~chan is considered to be the unofficial leader of Perfume because of her cheerful and energetic personality, and because she often acts as the MC at the group's concerts. She is sometimes very emotional and is known for crying a lot.
- Stage name: A~chan (あ～ちゃん), a-chan
- Full name: Nishiwaki Ayaka (西脇綾香)
- Birthdate: February 15, 1989
- Birthplace: Hiroshima, Japan
- Blood Type: A
- Height: 160cm
- Favorite things: Laughing, Talking, Walking, Make-Up, Korean Dramas, Winnie the Pooh
- Favorite foods and drinks: Fruits, Ice Cream, Mineral Water
- Favorite sports: Skating, Short Distance Run
- Favorite movie: Winter Sonata
- Favorite manga: B.O.D.Y.
- Favorite artists: Superfly, SPEED, aiko
- While all three members of Perfume are big fans of SPEED, A~chan is the biggest fan. She owns all of SPEED's CD's and photobooks, and cites hiro as being the reason she decided to become a singer.
- A~chan’s first crush went to a handshake event in Perfume's hometown Hiroshima, along with many other fans. When A-chan realized he came, she panicked, asking “What’s going on, why did you come!?!” in Hiroshima dialect.
- A~chan has a growing collection of 80 pairs of pajamas.
- A~chan has a younger sister who is also part of an idol group. She is Nishiwaki Sayaka of the female idol group, 9nine.