"Blue Bird" is the 40th single released by Ayumi Hamasaki. It was released on June 21, 2006. "Blue Bird" was Hamasaki's 15th consecutive single to top the Oricon and 27th #1 single in total. Initially planned to be a triple A-side single, it features two new songs, "Blue Bird" and "Beautiful Fighters". "Blue Bird" was the CM song for Zespri Gold Kiwifruit while "Beautiful Fighters" is featured on a Panasonic D-snap and D-dock commercial. A rearrangement of "Ladies Night", featured in her (Miss)understood album, called "Ladies Night (Another Night)" (which was featured in an earlier Panasonic Lumix commercial) is also featured on this single. A trance remix to "Blue Bird" is also on the single. On her official website, she describes "Blue Bird" as being a summer song, and "Beautiful Fighters" as being a song praising women. Blue Bird also reunited Hamasaki with the composer Dai. Blue Bird was the first time he composed a song for Hamasaki since "Will" (2005), which she co-composed under the name Crea. "Blue Bird" was Hamasaki's first single to be certified platinum since 2005's "Heaven" and was her last single to achieve platinum status until Mirrorcle World (2008). The sales of "Blue Bird" made Hamasaki the first solo artist in Japan to sell over 20 million singles.