"W-B-X (W-Boiled Extreme)"[A] (stylized as "W-B-X ～W-Boiled Extreme～") is the eleventh single by Japanese musical artist Aya Kamiki and the first as a collaboration with TAKUYA, former guitarist of Judy and Mary, as Aya Kamiki w TAKUYA (上木彩矢 w TAKUYA,Kamiki Aya w TAKUYA?). The song is Kamiki's first release under the Avex Trax label and is used as the opening theme for Kamen Rider W. It is also a single from her first album released under Avex titled Individual Emotion.
In its first day of release, the single sold 7000 copies and reached #8 on the Oricon daily charts. It also became the #1 theme song downloaded as a ringtone for the week of November 25 to December 1. The single has sold 54,176 copies during 27 weeks and has been downloaded more than 100,000 times (Gold) on mobile.