Yasuda Kei was born on December 6, 1980 in Futtsu, Chiba Prefecture to a couple whose name are undisclosed. She was two years old when she sang her first sing, "Echizen Misaki". At age 8, Yasuda compsed a song she called "Nagareboshi" (流れ星) for a competition.  At age 13, she joined the brass band club in junior high school playing the saxophone. She also participated in the Chibakentaikai tournament playing the saxophone.
In first grade high school, Yasuda got rid of her glasses and started using contacts. She went through a rebellious pahse as a Kogal hanging around Kisarazu. In second grade, Yasuda didn't want to go to school at all and quit in September. She started working part-time jobs at a convenience store, a famiresu, a stationary department and later at McDonald's.
After the second generation joined, Morning Musume went on to produce one album and three more singles until Fukuda Asuka decided to graduate in April 1999 to further pursue her studies. Yasuda was given almost all of Fukuda's lines in future performances of these early songs. She had also collaborated with other Morning Musume members in special projects during these early days. One of the more notable ones was when she co-wrote and co-sang with Abe Natsumi the song "Sanpo" for a radio contest. It became wildly popular and a petition was circulated to make it an official single, though that never did happen.
In 2000, the talk show "Utaban" was met with big controversy surrounding Ishibashi's "bullying" of Yasuda. She also obtained a moped license necessary for a commercial shooting.
On May 20, 2000, Yasuda appeared in the movie "Pinch Runner" which was released in theaters.
Yasuda was hospitalizatied due to illness early in the New Year. SHe also appeared in the stage play "LOVE Century".
Yasuda and Ichii sang a particularly catchy duet known as "Otome no Shinrigaku" for Morning Musume's second album. In response to the popularity, Tsunku decided to group them together with the third generation member, Goto Maki to create Morning Musume subgroup Petitmoni (also known as Pucchimoni) in 2001. Their first single, "Chokotto LOVE", has sold over a million copies since its release date.
She had also collaborated with other Morning Musume members in special projects during these early days. One of the more notable ones was when she co-wrote and co-sang with Natsumi Abe the song "Sanpo" for a radio contest. Kei Yasuda also performed a few self written songs on a radio show. Despite more fans requests for the songs to be released, they never were. They are titled "Nacchi wa nee" and "Dear My Friend", and were sung on air at "MBS Radio".
After Ichii graduated from Morning Musume and Petitmoni, fourth generation member Yoshizawa Hitomi was placed into the subgroup. Yasuda had taken on the role of leader of Petitmoni and the group continued to produce three singles and an album.
In March, Yasuda released her first and only photobook "Kei". It placed 7th in the photo book sales.
Yasuda graduated in May 2003, to concentrate on an acting career. At the same time when Morning Musume's 6th generation became full-fledged members. Tsunku commented that this one-time sixteen-member formation will be the largest Morning Musume will ever be. During her graduation concert, Yasuda sang a remixed rock version of "Never Forget", which was also Fukuda's graduation song. Additionally, as a special gift, Tsunku gave Yasuda a CD of her own soloist version of "AS FOR ONE DAY", her last single with Morning Musume. On the TV show MBS Song Town on July 3, 2015 Yasuda said Tsunku asked if she wanted to sing the full song, which she did, and then gave her the recording (she showed the mini disc on the show). Yoshizawa Hitomi followed up by saying that (a) this was the first time she heard about it and (b) she didn’t get something similar. Makoto mentioned rumors that later auditions required girls to show their forehead—Yajima said later in the program Tsunku told them, “if you don’t show your forehead you’ll look gloomy.” Yasuda jokes she wouldn’t have passed, and was told not to show her forehead. Tsunku mentioned in his 20th Anniversary interview that even though the camera focused on others, it was usually Yasuda singing.
Upon her graduation from the group, "Utaban" aired a one hour Kemeko SP special.
Following Yasuda's graduation, Iida was given the title of leader of Morning Musume and Yaguchi was given the title of sub-leader. Petitmoni's leadership was handed over to Yoshizawa, and two members were added (fifth generation Morning Musume member Ogawa Makoto and Coconuts Musume's Ayaka Kimura) and Goto was removed. This new line up of Petitmoni never had another release, but a few of their songs were featured on compilation albums.
A program called "Hello! Kids" (ハローキッズ), airing from 2002 to 2004, featured Yasuda in a segment series called "Bishoujo Senshi Oshienja" (美少女戦士オシエンジャー).
Yasuda is still in Hello! Project after graduation and has acted in dramas outside of H!P. Within H!P, she has collaborated with Nakazawa Yuko and other H!P artists on 2 Folk Songs albums, performed and MCed in Abe's first solo concert, sang backup for Goto Maki's single "Daite Yo! Please Go On," and had hosted Morning Musume's weekly TV show Hello! Morning until Ishikawa Rika took that position. Yasuda had participated in the H.P. All Stars single "ALL FOR ONE & ONE FOR ALL!" and the Puripuri Pink shuffle unit. Puripuri Pink was a new type of shuffle unit, since it was the first unit to feature graduated Morning Musume members, who were usually not included in the shuffles.
During a promotional appearance on Utaban in 2004, Yasuda revealed that she has been learning psychology, how to play golf, how to play the flute, and also that she is pursuing a career in the theater.
From May 23 to June 17, Yasuda appeared in the stage play "Youkihi no Kanpouyaku".
On March 31, 2009, Yasuda graduated from Hello! Project along with the rest of the H!P Elder Club.
On September 21, Kei had to have surgery to remove her tonsils. On her blog she revealed that she has had chronic tonsillitis since the time of her debut and and as a result has gotten fevers since then.
After graduating from Hello! Project in 2009, Yasuda has written several songs. The song Kimi ni Todoke was performed at fan club events, and the performance made it to a fan club dvd. It was also released as a digital download.
From July 20-25, Yasuda appeared in the stage play "Boku ni Niai no Karada".
In September of 2010, She joined the unit Afternoon Musume with 7 of her fellow OG members.
On February 15, theuflicks channel release the first episode of UF Licks show, where Yasuda, along with Tasaki Asashi, was the host for the episode. At the end of the event, she revealed that she will attend Forest For Rest ~SATOYAMA e Ikou~ SATOYAMA movement in YOKOHAMA on March 2nd and 3rd.
On May 29, Yasuda and Kozaki Yoichi registered their marriage and are now legally married.
On August 7, it was announced that Yasuda's father was reported missing. At an event, Yasuda said she hasn't been able to contact him in any way since May and filed a missing persons report with the police department in July. The police are currently searching for the man.
On December 14 and 15 Yasuda Kei and Ogawa Makoto hosted a Christmas Dinner show titled Yasuda Kei Ogawa Makoto Christmas Dinner Show 2013
On February 29, Yasuda and Yaguchi Mari were scheduled to hold a live event called "M-line club 10 Shuunen Kikaku 'Yasuda Kei, Yaguchi Mari' FC Event" (M-line club 10周年企画「保田圭・矢口真里FCイベント」), but it was later cancelled due to the COVID-19 pandemic.
On June 19, Yasuda, along with Iida Kaori and Tsuji Nozomi, attended an online event called "Mou Sugu Papa no Hi ~Papa to Mama no Iiwake!! Dousoukai Special~" (もうすぐパパの日!~パパとママのいいわけ!!同窓会スペシャル!~). It was streamed live on YouTube. It is tied up to the release of Tsunku's new childrens' book "Nee, Mama? Boku no Onegai!".
On August 28, Yasuda appeared at the presentation of the product Shiramen Wrinkle Duo .
On December 20, Yasuda was a guest at Goto Maki's Goto Maki 20th Anniversary SPECIAL ONLINE EVENT.
Yasuda was among the original OGs of Morning Musume to appear on Nakai Masahiro No Kinsuma, and picked right up with Ishibashi Takaaki when he made a surprise appearance in the studio. Yasuda relayed a heart felt message that she grew in popularity thanks to the antics of Utaban and had a sizeable segment dedicated to her during this special.
- Yasuda has a little brother who was born when she was 9 years old.
- Her parents divorced in April 2012.
She dropped out of school after her first year in high school. She worked part-time jobs when auditioning for Morning Musume.
Is good friends with fellow second generation member Yaguchi Mari.
- Birth/Stage Name: Yasuda Kei (保田圭)
- Legal Name: Kozaki Kei (小崎圭)
- Date Married: May 29, 2012
- Nickname: Kei-chan (圭ーちゃん), Kemeko, Yasusu, "Aunty", Yasuda-daimyoujin (Yasuda-high-priestess)
- Birth Date: December 6, 1980
- Birth Place: Futtsu, Chiba, Japan
- Blood Type: A
- Height: 158.5 cm (5 ft 2.4 in)?
- Western Zodiac: Sagittarius
- Eastern Zodiac: Monkey
- Hello! Project Status:
- 1998-05-03: Member
- 2003-05-05: Graduated Morning Musume
- 2009-03-31: Graduated
- UP-FRONT GROUP Status:
- Years in Morning Musume: 5 Years
- Dream Morning Musume Color: Yellow-Green
- Hello! Project Groups:
- Concert Units:
- Shuffle Units:
- Other Groups:
- Main article: Yasuda Kei/Discography
- Digital Singles
- [2009.12.10] Kimi ni Todoke
- Fanclub Singles
-  LOVE -Keisan Chigai-
- Other Singles
- Other Albums
- [2001.11.29] The Douyou Pops 1 Christmas to Fuyu no Uta Shuu
- [2002.02.20] The Douyou Pops 2 Haru no Uta Shuu
- [2002.06.05] The Douyou Pops 3 Natsu no Uta Shuu
- [2002.09.04] The Douyou Pops 4 Aki no Uta Shuu
- [2002.12.04] Shinsaku Douyou Pops 1
- [2003.03.26] Shinsaku Douyou Pops 2
- [2003.05.21] FS4 FOLK SONGS 4
- [2004.02.25] FS5 Sotsugyou
- [2003.10.29] Hello! Project Radio Drama Vol. 1
- [2006.07.26] Hello! Project Radio Drama Osaka-hen Vol. 3
- [2008.12.03] GUILTY PLEASURES 3 (#4 Love Machine)
- Unreleased Songs
-  Nacchi wa Nee. (なっちはねぇ。; You See, Nacchi She.)
-  Dear My Friend
-  Happy (with Yaguchi Mari)
-  Mou Ichido ~I miss you~ (もう一度〜I miss you〜; One More Time ~I Miss You~)
-  Kimi e no Uta ~Always Love~ (きみへのうた〜Always Love～; A Song to You ~Always Love~)
- Group Songs
- [2002.03.27] Hajimete no Rock Concert (with Iida Kaori, Yaguchi Mari, Goto Maki, Tsuji Nozomi, and Ogawa Makoto
- [2003.03.26] YES! POCKY GIRL (with POCKY GIRLS)
- [2003.03.26] "Sugoku Suki na no ni…ne" (with Iida Kaori, Abe Natsumi, Yaguchi Mari, Ishikawa Rika, and Yoshizawa Hitomi)
- [2011.04.20] Roman ~MY DEAR BOY~ (Morning Musume cover; with Abe Natsumi, Yaguchi Mari, Yoshizawa Hitomi, and Ogawa Makoto)
- [2011.04.20] Morning Coffee (2011 Dreamusu Ver.) (Morning Musume cover; with Nakazawa Yuko, Iida Kaori, Abe Natsumi, and Yaguchi Mari)
- [2011.04.20] SEXY BOY ~Soyokaze ni Yorisotte~ (Morning Musume cover; with Nakazawa Yuko, Iida Kaori, Abe Natsumi, and Yaguchi Mari)
- [2002.03.02] Kei
- [2014.04.20] Bibusukon - Saikai Musume. No Konkatsu Monogatari -
- [2005.05.02-2005.02.10] Yasuda Kei, Inaba Atsuko Casual Dinner Show (保田圭・稲葉貴子カジュアルディナーショー)
- [2005.05.14-2005.05.15] Yasuda Kei, Inaba Atsuko, Ayaka no 1-Paku 2-Nichi Bus Ryokou in Nagano
- [2006.06.10-2006.06.11] Yasuda Kei, Inaba Atsuko, Ayaka no 1-Paku 2-Nichi Bus Ryokou in Nagano Part 2
- [2007.06.02-2007.06.03] Yasuda Kei, Inaba Atsuko, Ayaka no 1-Paku 2-Nichi Bus Ryokou in Nagano Part 3
- [2007.02.11-2007.02.12] Yasuda Kei, Inaba Atsuko Casual Dinner Show (保田圭・稲葉貴子カジュアルディナーショー)
- [2020.02.29] M-line club 10 Shuunen Kikaku 'Yasuda Kei, Yaguchi Mari' FC Event (cancelled)
-  Morning Cop ~Daite HOLD ON ME!~ (モーニング刑事。～抱いてHOLD ON ME!～)
-  Pinch Runner (ピンチランナー)
-  Tokkaekko (とっかえっ娘。)
-  Koinu Dan no Monogatari (子犬ダンの物語)
-  Morning Musume no Heso
- [2000.01.04-2000.03.29] Morning Musume no Koimonogatari
-  Friday Night wa Onegai! Morning (フライデーナイトはお願い!モーニング)
- [2000-2007] Hello! Morning
- [2002-2004] Hello Kids (ハローキッズ)
-  Bishojo kyoiku II (美少女教育II)
-  Futarigoto (二人ゴト)
-  Uta Doki! ~Pop Classics~
-  Izu no Odoriko (伊豆の踊子)
-  Kochira hon ikegami sho (こちら本池上署)
-  Mikeneko Holmes no Hanzaigaku Kouza (三毛猫ホームズの犯罪学講座)
-  Tokio-chichi he no Dengon (トキオ 父への伝言)
-  Nijyuushi no Hitomi (二十四の瞳)
-  Shinjuku no haha monogatari (新宿の母物語)
-  Sousa Ikka - Ken atari han, Takako no manako (捜査一課･見当たり班 鷹子の眼)
-  Suugaku♥Joshi Gakuen (数学♥女子学園)
-  Mikkai no yado 9 hoseki no amai wana (密会の宿9 宝石の甘い罠)
-  Shiawase no jikan (幸せの時間)
-  Sho kyoto renzoku satsujin jiken x Gekai hatomura shugoro (小京都連続殺人事件×外科医 鳩村周五郎)
-  Rashomon ~Onnatachi no Maboroshi~ (羅生門～女たちのまぼろし～)
-  Natsu no Yoru no Yume (夏ノ夜ノ夢; Shakespeare's "Midsummer Night's Dream")
-  Otona no Mugicha Dai kyu hai me Kouen "Nemurenaito" (大人の麦茶第九杯目公演「ネムレナイト」)
-  MAMA LOVES mambo IV
-  Showa kayo shiata shinjuku no onna (昭和歌謡シアター新宿の女)
-  Yokihi no kanpoyaku (楊貴妃の漢方薬)
-  Shinjuku no Onna (新宿の女)
-  Chigaimasu sisters (ちがいますシスターズ)
-  COASTER（Coaster） (COASTER（コースター）)
-  Shishi tachi (志士たち)
-  THE do tsubo!!! (THEどツボッ!!)
-  Lemon Star (レモンスター)
-  Mikoto Mannequin (ミコトマネキン)
-  Every Little Thing '09 (エブリ リトル シング '09)
-  Romantic ni yoroshiku (ロマンチックにヨロシク)
-  Momoiro shoten e yokoso (桃色書店へようこそ)
-  Murder Factory (マーダーファクトリー)
-  Nemure nu yoru no 1 x 8 requiem ~Naked police academy~ (眠れぬ夜の1×8レクイエム〜ネイキットポリスアカデミー〜)
-  Boku ni Niai no Karada (僕に似合いの身体)
-  Ii hi, risutora (いい日、リストラ)
-  Jinsei wa Show Time! (人生はショータイム！)
-  Genji monogatari x Oguro Maki songs ~Boku wa jūnihitoe ni koi wo suru~ (源氏物語×大黒摩季songs〜僕は十二単に恋をする〜)
-  Amakara (あまから)
-  Abe Naikaku (安倍内閣)
-  Sarachi 5 (更地5)
-  Nemureru mori no bijo (眠れる森の美女)
-  Sarachi 6 (更地6)
-  B・B~bumpy buddy~
-  Tabidachi ~Ashoro yori~ (旅立ち〜足寄より〜)
-  Aoge ba (あおげば)
-  I.have.a.dream (アイ・ハヴ・ア・ドリーム)
-  Bokutachi Karen na Shounen Gasshoudan
- [1998-1999] Morning Musume no onegai MORNING CALL! (モーニング娘。のお願いMORNING CALL!)
- [1999-2000] Pucchimoni Diver (プッチモニダイバー)
- [2001-2002] Pucchimoni Driver V3 (プッチモニダイバーV3)
- [2000-2002; 2009–] Young Town Doyoubi (ヤングタウン土曜日)
- [2016–2017] HELLO! DRIVE! (HELLO! DRIVE! -ハロドラ-) (Wednesdays)
- [2013-] UF LICKS
-  Glico Mousse Pocky
-  Fuku Pika (フクピカ)
- Yasuda is skilled in several musical instruments, including the saxophone and the piano.
- She has made several appearances on TV and in concert accompanying herself or others.
- On a variety show she mentioned that when she finally would get a solo part of a song, she'd work really hard on that certain part when they would shoot the MV's or whenever they performed the song on variety shows. However, she was very frustrated on how producers would usually center Abe Natsumi on the camera for most of the time even if all of Morning Musume was singing togethor. She says a way that she could get on camera was if she slyly appeared behind Abe when the camera was focused on her. Tsugunaga Momoko noted that she and others who were kouhai's of Morning Musume would analyze these occurrences and implement them when they also appeared on stage.
- On that same variety show she mentioned that Goto Maki and Abe Natsumi received many presents and letters during their handshake events however, Yasuda would only get 2 or few.
- Yasuda wrote a kaeuta (parody song) in 2010, where she complained about wanting to be center for at least one of Morning Musume’s singles, but she never got to be.
- Yasuda attended Kimitsu Shogyo (Commercial) High School in Futtsu City, Chiba Prefecture, but dropped out to pursue her dreams in the entertainment industry.
- She worked in a McDonald's restaurant in her hometown, until 1998.
- She is the third oldest girl to join Morning Musume after its formation and the oldest to join under normal circumstances (Fujimoto Miki of the 6th generation was added to Morning Musume after failing the 4th generation audition and was brought back as a soloist before being added, and 8th generation member Junjun was added after an audition that was not even known by the members of the group themselves.).
- She was famously known as the "grandma" of Morning Musume, and was the frequent target of jokes from TV hosts and other members.
- She is best friends with Yaguchi Mari.
- Had a youkai Yasuda Doll made for her on Utaban.
- She is the third former Morning Musume member to only graduate from Morning Musume and not Hello! Project. The first being Nakazawa Yuko and the second being Goto Maki.
- Appears in the TV Drama Suugaku♥Joshi Gakuen together with Iida Kaori as the Devil Sisters.
- She was the only Morning Musume sub-leader who never became leader. In 2018, Iikubo Haruna became the second former sub-leader to never become leader.
- She is the last 2nd Generation member to get married.
- Her son (born on January 7, 2018), shares his birthday with fellow Morning Musume member Ishida Ayumi (January 7, 1997) who was born 21 years prior.
- When Yasuda was in Morning Musume, she was made fun of for her wink-style.
- The first CD Yasuda bought was by Sharan Q.
|Oldest Member of Petitmoni
October 3, 1999 – 2002
|Sub-leader of Morning Musume
April 16, 2001 – May 5, 2003
|Oldest Member of Morning Musume
April 16, 2001 – May 5, 2003
|Sub-leader of Hello! Project
May 5, 2003 – March 31, 2009
|Hello! Project Shuffle Units|