WIKIPEDIA:

“ was the first official subgroup of Japanese pop girl group Morning Musume formed in November 1998. They specialized in singing slow and mature songs, which morphed to an old-fashioned and upbeat style—a genre somewhat similar to that of the band from which it originated.

History
The group was founded in November 1998, consisting of three Morning Musume members: Aya Ishiguro, Kaori Iida, and Mari Yaguchi. After the formation, the group immediately released their first single, "Last Kiss," which was used on the anime Sorcerous Stabber Orphen. The single has a "sexy" vibe that they used on their second single and first album. However, they created a fresh image when they released "Tanpopo". This new image did not become as popular as the first image they had created.
After the release of the group's fourth single, Aya Ishiguro graduated from Morning Musume and left the group. The remaining members continued performing their songs in concerts as Generation 1.5 Tanpopo.
On June 2000, Morning Musume 4th Generation members Rika Ishikawa and Ai Kago joined Tanpopo, making the two-member group a four-member group. The style of their songs changed also when the four released "Otome Pasta ni Kandō." The style of this song became analogous to [......] ”

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