During her time with Morning Musume, her solo line "Sexy Beam" from their 2000 single "Koi no Dance Site" became a media phenomenon and became closely associated with her.

[2][3] She left the group in 2002 after the release of Mini-Moni the Movie: Okashi na Daibōken!, which explained a fictional account behind her reasons for leaving.

Yaguchi abruptly resigned from Morning Musume in April 2005 after her relationship with Shun Oguri went public in the media, stating that the incident affected her ability to uphold the group's idol image,[4] as the members were not allowed to date.

Yaguchi's first solo recording, "Nigiyaka na Fuyu," a collaboration with Berryz Kobo, appears as the coupling track on Berryz Kobo's November 2005 single "Gag 100kaibun Aishite Kudasai" for Futari wa Pretty Cure Max Heart the Movie 2: Friends of the Snow-Laden Sky.

[6] Yaguchi was also one of the main actors in the Japanese daytime drama series Gal Circle (ギャルサー, Garusaa).

[citation needed] Following the popularity of singles and an album released in conjunction with the Japanese variety program Quiz!

Hexagon II (クイズ!ヘキサゴンII), Yaguchi released her debut solo single, "Seishun Boku/Seishun Ore" (青春 僕/青春 俺), on March 25, 2009.

In 2013, Yaguchi decided to retire from entertainment following backlash from her extramarital affair and divorce from actor Masaya Nakamura.

Umeda had canceled his social internet accounts without explanation in early March, but he denied doing anything wrong following the Josei Seven report.

One of the commercials she filmed post-divorce involved her making self-deprecating jokes about her divorce, which was pulled off air after complaints.