|Native name||佐藤 優樹|
|Born||May 7, 1999|
|Other names||Masaki (まさき?)
In 2011, Masaki participated in the 10th generation auditions for Morning Musume. Throughout September, she appeared weekly on the TV show Hello Pro! Time in the segment dedicated to the auditions.
On September 29, 2011, at a concert at Nippon Budokan, which was part of Morning Musume Concert Tour 2011 Aki Ai Believe: Takahashi Ai Sotsugyō Kinen Special, it was announced that Masaki Sato passed the auditions alongside 3 other girls: Haruna Iikubo, Ayumi Ishida, and Haruka Kudo.
On April 18, it was announced that Tanaka Reina and the 9th & 10th Generation members would participate in a new stage play titled Stacey's Shoujo Saisatsu Kageki. The musical ran from June 6-12.
During the last few days of her first concert tour, she cut her hair short.
On May 13, information was released about an event for the 9th and 10th generation members of Morning Musume as well as S/mileage’s 2nd generation members, titled Mosuma FC Event ~Gachi☆Kira~. It took place on June 15th, 18th, and 20th at Yokohama Blitz.
On October 10, it was announced that Sato would be a member of the new unit Harvest alongside Ikuta Erina, Ishida Ayumi, and Takeuchi Akari.
On January 11, 2013, it was released that Sato Masaki, who has been resting since December 31st due to a high fever, has been diagnosed with left neck cervical lymphadenitis after a detailed examination. She was absent for all events between December 31 through January 17.
On May 7, Sato had her birthday event, titled Sato Masaki Birthday Event ~14 sai nau nauuuu!!~. Guest included fellow 10th generation member Kudo Haruka.
On July 23, it was announced that Sato would be a member of the new unit Jurin alongside Juice=Juice member Miyamoto Karin.
On March 13, it was announced that Sato would be a member of a newly formed SATOYAMA movement unit called Sato no Akari.
On May 7, Sato celebrated her 15th birthday. This special event was called Morning Musume '14 ~Sato Masaki Birthday Event 2014~. It featured two performances in Tokyo.
Hello! Project groups and units
- Morning Musume (2011–present)
- Hello! Project Mobekimasu (2011)
- Harvest (2012–present)
- Jurin (2013–present)
- Satonoakari (2014–present)
- Morning Musume
- "Pyoco Pyoco Ultra" (January 25, 2012 )
- "Ren'ai Hunter" (April 11, 2012 )
- "One Two Three / The Matenrō Show" (July 4, 2012 )
- "Wakuteka Take a Chance" (October 10, 2012 )
- "Help Me!!" (January 23, 2013 )
- "Brainstorming / Kimi Sae Ireba Nani mo Iranai" (April 17, 2013 )
- "Wagamama Ki no Mama Ai no Joke / Ai no Gundan" (August 28, 2013 )
- "Egao no Kimi wa Taiyō sa / Kimi no Kawari wa Iyashinai / What is Love?" (January 29, 2014 )
- "Toki o Koe Sora o Koe / Password is 0" (April 16, 2014 )
- "Tiki Bun / Shabadaba Dū / Mikaeri Bijin" (October 15, 2014 )
- "Seishun Kozo ga Naiteiru / Yūgure wa Ameagari / Ima Koko Kara" (April 15, 2015 )
- "Oh My Wish! / Sukatto My Heart / Ima Sugu Tobikomu Yūki" (August 19, 2015 )
- "Tsumetai Kaze to Kataomoi / Endless Sky / One and Only" (December 29, 2015 )
- "Utakata Saturday Night! / The Vision / Tokyo to Iu Katasumi" (May 11, 2016 )
- "Sou Janai / Sexy Cat no Enzetsu / Mukidashi de Mukiatte" (November 23, 2016 )
- Sūgaku Joshi Gakuen (January 11, 2012 — March 28, 2012 ) as Rion Miyamasu
- Hello Pro! Time (ハロプロ!TIME?) (September 2011 —)
- Morning Musume Concert Tour 2011 Aki Ai Believe: Takahashi Ai Sotsugyō Kinen Special (コンサートツアー2011秋 愛BELIEVE～高橋愛 卒業記念スペシャル～?) (September 2011)
- Hello! Project 2012 Winter Hello☆Pro Tengoku: Rock-chan
- Hello! Project 2012 Winter Hello☆Pro Tengoku: Funky-chan
- Morning Musume Concert Tour 2012 Haru: Ultra Smart (February 18, 2012 — May 13, 2012 )
- モーニング娘。10期メンバー 決定！ (in Japanese). Up-Front DC Co., Ltd. 2011-09-30. Archived from the original on 2014-04-01. Retrieved 2016-07-25.
- モーニング娘。新メン発表＆高橋愛5期メン再集結に涙の熱唱 (in Japanese). Plantech Co., Ltd. 2011-09-30. Retrieved 2011-09-30.
- 終わったよー！. Kanon Fukuda (in Japanese). Kanon Fukuda's official ameblo blog. 2011-10-29. Retrieved 2012-02-20.
- モーニング娘。10期メンバー4人発表 明日卒業の高橋愛は「進化」に期待 (in Japanese). Oricon Inc. 2011-09-29. Retrieved 2011-09-30.
- 数学女子学園｜日本テレビ (in Japanese). Nippon Television. Retrieved 2012-02-20.
- on YouTube
- Morning Musume's Michishige Sayumi is surprised: "A member who is an elementary school student knows how to use an iPad!" - J-CAST, Inc., January 26, 2012 (Japanese)
- Masaki Sato profile on the Hello! Project official site (Japanese)
- Masaki Sato profile at the Sapporo model agency MIST K's COMPANY (Japanese)