Duo U&U (デュオU&U, Duo U&U) is the first album by W, the duo formed by Morning Musume and Minimoni members and longtime friends Ai Kago and Nozomi Tsuji. Recorded while they were winding down their duties as Morning Musume and Minimoni members, the album consists of cover versions of songs released by other female Japanese pop duos from the later Showa period, including covers of songs by The Peanuts, Pink Lady, and Wink. The idea was that W were continuing the tradition that the original artists they covered on this album established, as well as give fans of Kago and Tsuji that had never heard the original recordings a taste of Japanese pop history.

W promoted the album in Japan with a variety of TV appearances, including a June 2004 special during which they performed alongside Pink Lady as both W and as part of Morning Musume. W and Pink Lady performed the latter's "Southpaw" while the full Morning Musume contingent and Pink Lady performed "Nagisa no Sinbad" and a medley of Morning Musume's "LOVE Machine" and Pink Lady's "S.O.S.".

At the end of July 2004, W "graduated" from (i.e. performed their final concert as members of) Morning Musume, allowing them to concentrate on W full-time. Duo U&U would be the only W album containing all classic J-pop covers, as future single releases would be originals composed by Tsunku and their follow-up album, 2nd W, would contain a mix of original material and more classic J-pop covers.

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