She is the first person to join Morning Musume that is fluent in English, and since her joining, she has been appointed the role as the group's "global representative" (グローバル担当; global tantou).
Nonaka Miki was born on October 7, 1999, in Shizuoka, Japan. Due to her father's job, she lived in the United States for eight years. She lived in the state of Illinois from 2001 to 2004 and in the state of Alabama from 2004 to 2010. During her time in Alabama, she attended Applause fine arts school.
In summer 2014, Nonaka took part in the Morning Musume '14 <Golden> Audition! and successfully passed. Her audition number was #269. She was introduced as a 12th generation member during Morning Musume '14's concert at Nippon Budokan on September 30 alongside Ogata Haruna, Makino Maria and Haga Akane.
On January 4, Nonaka and and her fellow 12th generation members began a radio show on FM FUJI, titled Morning Musume '15 12ki Nikki. They also began a web talk show exclusive to fanclub members on March 5, titled 12ki Relay.
On June 12, Nonaka released her first solo e-Hello! Blu-ray, Greeting ~Nonaka Miki~.
On October 7, Nonaka celebrated her 16th birthday at a fanclub event Morning Musume '15 Nonaka Miki Birthday Event, featuring three shows at TOKYO FM HALL.
On January 29, Nonaka held a talk event at the Hello! Project Official Shop in Akihabara.
On February 10, it was announced that Nonaka injured her left foot during a dance rehearsal for the Morning Musume '16 Concert Tour Haru ~EMOTION IN MOTION~. After seeing a doctor, she was diagnosed with an avulsion fracture of the base of the fifth metatarsal (dancer's fracture) and a ligament injury in her heel. Nonaka required 4 weeks of recovery, and was not able to participate in several events during the month of February. As of February 20, Nonaka was able to sing while sitting.
On February 12, it was announced that Nonaka would provide the English narration for Shizuoka Asahi TV's annual music documentary program ch223 music pinkiss ~Ponyo Trio Nihon Ichi no Sotsugyou Ryokou!?~, featuring Country Girls member Yamaki Risa and Hakoiri♡Musume member Wagatsuma Momomi. The original Japanese narration was broadcast February 20, and Nonaka's English narration was broadcast on February 26.
On May 3, Nonaka began the monthly radio show Hello! Project Mobile Sendenkaigi for the Hello! Project Mobile service along with "promotion manager" Kudo Haruka and fellow "promotion staff" members Ogata Haruna and Yanagawa Nanami.
On October 21, Nonaka celebrated her 17th birthday at a special event called Morning Musume '16 Nonaka Miki Birthday Event, featuring one show at Kameari Lirio Hall in Tokyo.
On January 1, Nonaka announced that as a global representative of Hello! Project and Morning Musume she would be making English videos about Hello! Project for the UP-FRONT LINK Facebook page throughout 2017.
On February 14, Nonaka announced on her blog that she would star in her first drama, an episode of Otona e Novel on February 23.
On April 6, the Morning Musume '17 12th generation and 13th generation members began a radio show on FM FUJI, titled Morning Musume '17 no Morning Diary.
On October 19, Nonaka celebrated her 18th birthday at a fanclub event titled Morning Musume '17 Nonaka Miki Birthday Event, featuring two shows at IMA Hall.
On February 5, it was announced that RakutenTV, who made a deal with the NBA last October for exclusive online distribution rights in Japan, have appointed Nonaka as an official NBA ambassador and she has traveled to New York City for her first week of training. She would be working alongside former Berryz Koubou member Tokunaga Chinami, who had been studying English abroad. On February 19, Nonaka announced that she was the ambassador for the Los Angeles Lakers.
On June 4, the 12th generation members held the Morning Musume '18 12ki Member Ogata Haruna・Nonaka Miki・Makino Maria・Haga Akane FC Event at Differ Ariake.
On October 9, Nonaka celebrated her 19th birthday at a fanclub event titled Morning Musume '18 Nonaka Miki Birthday Event, featuring two shows at Mynavi BLITZ Akasaka.
On December 13, it was announced that Nonaka would be halting idol activities until mid-February 2019 to study abroad as a short term student to improve her English skills. She left Japan at the end of December and would continue updating her blog during her time abroad.
On December 21, Nonaka announced that her work as a Rakuten NBA 32 ambassador would conclude at the end of year.
In the first performance of Hello! Project 2019 SUMMER tour held on July 13, Nonaka was only able to sing while sitting and had to wear sunglasses due to her catching pink eye in both eyes. However, she quickly recovered and was able to fully participate in the next day's performance.
On October 7, she celebrated her 20th birthday at a fanclub event titled Morning Musume '19 Nonaka Miki Birthday Event, featuring two shows at Mynavi BLITZ Akasaka.
On October 7, she celebrated her 21st birthday at a fanclub event titled Morning Musume '20 Nonaka Miki Birthday Event with two shows at LANDMARK HALL. In compliance with government policy, cheering, crowding, standing, and closeness in the venue were prohibited, and wearing masks were required to enter.
On October 7, she celebrated her 22nd birthday at a fanclub event titled Morning Musume '21 Nonaka Miki Birthday Event with two shows at LANDMARK HALL. In compliance with government policy, cheering, crowding, standing, and closeness in the venue were prohibited, and wearing masks were required to enter.
On October 23, a show personally produced by Nonaka aired at 16:00 JST on TV Asahi Channel 1 as her prize for winning MVP at Hello! Project presents... "Solo Fes! 2". It was titled Miki Nonaka presents... Morning Musume '21 ~SONGS FOR YOU~.
When Nonaka joined Morning Musume in September 2014, she was in her third year of middle school. She graduated from middle school on March 20, 2015. She started high school in April 2015 and graduated in March 2018.
In September 2013, she took the Test of English for International Communication (TOEIC) at her school in Shizuoka, which she scored 795 on the exam. She is also grade 2 in the EIKEN Test in Practical English Proficiency (STEP Eiken).On October 7, 2020, the day of her 21st birthday, she revealed that she has been studying at Waseda University's online school.
The following list are notable friendships Nonaka Miki has acquired:
- Ogata Haruna: Nonaka met Ogata Haruna when she joined the 12th generation and became close friends since. Her pairing name with Ogata is HaaChel (はーちぇる).
- Oda Sakura: She also is good friends with Oda Sakura. 
- Morito Chisaki: She gets along well with Country Girls member Morito Chisaki.
- Kamikokuryo Moe: She often goes out for meals and talks with ANGERME member Kamikokuryo Moe.
Nonaka's given name, Miki, means "beauty" (美; mi) combined with "rare" (希; ki).Her parents chose it by number of strokes and because they had many acquaintances with the name "Miki" who were a cute or wonderful person. Once they decided on the sound of Miki, they wanted kanji with stroke counts that were all had excellent luck, so they asked Nonaka's grandfather who knew a lot about it to choose.
Here is a list of nicknames that have been used to refer to Nonaka Miki:
- Chel (チェル): Her first official nickname which is used by fans. It is short for Chelsea (チェルシー), which was given to her by Oda Sakura. Oda gave her the nickname because Nonaka listed in her audition papers that her favorite candy was Meiji's Chelsea.
- Nonaka-chan (野中ちゃん / のなかちゃん): Her second official nickname which is used by classmates, members, and fans. In her nickname, "naka" has a strong intonation.
- Mikitty (ミキティ): A nickname given to her by Tsunku which is rarely used by fans due to Mikitty already being well known as the nickname of former Morning Musume member Fujimoto Miki. Nonaka first introduced herself with it during the Morning Musume '14 Concert Tour Aki GIVE ME MORE LOVE ~Michishige Sayumi Sotsugyou Kinen Special~ concert at Nippon Budokan on October 1, 2014.
- Name: Nonaka Miki (野中美希)
- Nicknames: Chel (チェル), Nonaka-chan (野中ちゃん)
- Birthdate: October 7, 1999
- Birthplace: Shizuoka, Japan
- Blood Type: A
- Height: 157 cm (5 ft 1.8 in)?
- Western Zodiac: Libra
- Eastern Zodiac: Rabbit
- Audition Song: "The Climb" by Miley Cyrus
- Hello! Project Status:
- 2014-09-30: Morning Musume member
- Years in Morning Musume: 6 Years
- Morning Musume Member Color:
- Hello! Project Groups:
- Other Groups:
- Main article: Nonaka Miki/Discography
-  Swing Town
-  Message (メッセージ)
- [2015.06.12] Greeting ~Nonaka Miki~ (e-Hello! Blu-ray)
Solo Fanclub DVDs
- [2018.02.22] Morning Musume '17 Nonaka Miki Birthday Event
- Main article: Nonaka Miki/Publications
-  TRIANGLE
-  Zoku 11nin Iru! Higashi no Chihei, Nishi no Towa
-  Pharaoh no Haka
-  Pharaoh no Haka ~Hebi Ou Sneferu~
- [2014–2019] The Girls Live
-  ch223 music pinkiss ~Ponyo Trio Nihon Ichi no Sotsugyou Ryokou!?~ (ch223 music pinkiss 2016 ～ポニョトリオ 日本一の卒業旅行!?～) (English narration)
- [2019–2020] AI・DOL PROJECT (AI・DOL プロジェクト)
- [2019–2020] Hello Pro! TOKYO Sanpo (ハロプロ!TOKYO散歩)
-  Hello! Project presents... "Solo Fes!"
-  Hello! Project presents... "Solo Fes! 2"
-  Miki Nonaka presents... Morning Musume '21 ~SONGS FOR YOU~
- [2017.02.23] Otona e Novel (オトナヘノベル)
- [2014–] Hello! Project Station
- [2014–2016] MUSIC+
- [2015–2016] GREEN ROOM
- [2016–] Upcoming
- [2016–2017] Girls Night Out
- [2017–] tiny tiny
- [2018–] OMAKE CHANNEL
-  Hello Pro no Monohon!
- [2019–2020] Hello Pro no Oshigoto Challenge
-  Hello Pro Kouhaku Taiko THE☆BATTLE 2019
-  Hello Pro ONE×ONE
-  Hello! Anison Bu
- [2015–2017] Morning Musume '17 12ki Nikki! (モーニング娘。’17 12期日記！)
- [2015–2017] 12ki Relay (12期リレー) (fanclub exclusive)
- [2016–] Hello! Project Mobile Sendenkaigi (ハロ！モバ宣伝会議) (Hello! Project Mobile exclusive)
- [2016–2019] HELLO! DRIVE! (HELLO! DRIVE! -ハロドラ-) (Mondays, 2016.09–2017.09; Wednesdays, 2017.10–2019.06)
- [2017–] Morning Musume '19 no Morning Diary (モーニング娘。'19のモーニングダイアリー)
- [2018–] Morning Musume '19 no Morning Jogakuin ~Houkago Meeting~ (モーニング娘。'19のモーニング女学院〜放課後ミーティング〜)