- Name: Matsunaga Riai (松永里愛)
- Nickname: Riai-chan (りあいちゃん)
- Birthdate: July 7, 2005
- Birthplace: Osaka, Japan
- Height: 150cm
- Specialties: Tongue twisters
- Hobbies: Listening to Hello! Project music, playing with her dog/animals
- Looks Up To: Sato Masaki, Sasaki Rikako
- Hello! Project groups:
Matsunaga Riai acted as a junior model for Dream Girls magazine prior to joining Hello Pro Kenshuusei. During March 2016 she was one of seven girls to recieved the Special Award in the 2016 JuniAward by HarajukuMate modeling competition; the same year in the fall she participated in and failed the "Morning Musume '16 Shinseiki Audition".
On March 6, 2017 she was revealed as a new member of Hello Pro Kenshuusei through an announcement on the official Hello! Project website, alongside Shimakura Rika, Hibi Marina, Eguchi Saya, Doi Rena, Okamura Minami, Yamada Ichigo, and Nakayama Natsume. She made her first live appearance several days later on March 11, at the "Hello Pro Kenshuusei Happyoukai 2017 3gatsu ~Marching!~" event.
On May 4, 2019 she won Best Performance with 419 audience votes during the "Hello! Project Kenshuusei Happyoukai 2019 ~Haru no Koukai Jitsuryoku Shindan Test~" event, for her performance of "Gatamekira" by Taiyou to Ciscomoon. The following month on June 14, 2019 she was revealed to be one of two new members of Juice=Juice, along with Hello Pro Kenshuusei Hokkaido member Kudou Yume, through a special premiere on the group's YouTube channel. Their first appearance with the group would take place on June 17 at Miyazaki Yuka's graduation Budokan concert.
- TV Dramas
-  Yuganda Hamon (歪んだ波紋)
- [2019–] Hello! Station (ハロ！ステ)
- [2019–] Upcoming (アプカミ)
-  Hello Pro Kouhaku Taiko THE☆BATTLE 2019 (ハロプロ紅白対抗 ザ☆バトル2019)
-  Hello Pro no Oshigoto Challenge! 2 (ハロプロのお仕事チャレンジ!2)
-  Hello Pro no Collabo NIGHT! (ハロプロのコラボNIGHT!)
-  Harukanaru Toki no Naka de 6 Gaiden ~Tasogare no Kamen~ (遙かなる時空の中で６ 外伝 ~黄昏ノ仮面~) (guest)
- Has an older brother and a younger sister, a model named Nanoa (なのあ).
- Has a Bernese Mountain Dog named Chloe and two cats, Taiga and Bibi.
- Has won her school's girls division marathon race for 5 years in a row.
- Attended an ANGERME handshake event before joining Hello Pro Kenshuusei.
- Met generation mates Doi Rena, Nakayama Natsume, and Okamura Minami prior to them joining Hello Pro Kenshuusei; having met Minami while modeling fpr "Dream Girls" magazine.
- Her favorite genre of music is J-Pop, mainly Hello! Project.
- Favorite sport is dance.
- Favorite food is waffles made by her mother.
- Her motto is "Futou fukutsu" (不撓不屈; Never stray from one's path).
- Thinks her charm point is her long hair.
- Her favorite school subject is music.
- Her favorite colors are yellow and emerald green.
- Isn't good with being scolded, baksetball, and insects.
- Thinks both her strength and her shortcoming is being serious.
- Her favorite Hello! Project songs are "Do it! Now" by Morning Musume, Rock no Teigi by Tanaka Reina, and Koi no Jubaku by Berryz Kobo.