Niji (AAA song)

"Niji" (虹, meaning "Rainbow") is the 16th single released by the Japanese pop group AAA. It was released on September 19, 2007, as the second of their "AAA DEN-O form" collaborations, tying in with the Kamen Rider Den-O franchise. The single featured the song "Niji," which served as the theme song for the Kamen Rider Den-O & Kiva: Climax Deka movie.

The single was released in two versions: a CD+DVD edition and a CD-only edition. The CD+DVD version included the music video for "Niji." The CD-only version featured a bonus track.

"Niji" is a J-Pop song known for its upbeat tempo and positive lyrics, reflecting the themes of hope and perseverance often associated with the Kamen Rider series. The song is typically performed live by AAA, and has become a popular song in their discography. The members' individual vocal parts contribute to the overall energy and emotional impact of the song.

The single charted on the Oricon charts, and contributed to AAA's growing popularity within the Japanese music scene. "Niji" remains a recognizable and well-regarded song, particularly among fans of both AAA and Kamen Rider.