Folder 5 (Japan) was a spinoff group from another J-pop group, Folder, also signed to Avex Trax. Along with the five girls, Folder also had two male members, Daichi and Joe. When Daichi and Joe left the group due to puberty, Folder became Folder 5. In 2000 they released their first single, "Supergirl". Their third single, "Believe", was used as the second opening theme for the popular anime One Piece. The song "Ready!" from their forth single "Stay..." was used as the theme song in the short "Jango's Dance Carnival" that was shown with One Piece's second movie, "Clockwork Island Adventure".