- Name: Eguchi Saya (江口紗耶)
- Nickname: Sayarin (さやりん)
- Birthdate: August 1, 2003
- Birthplace: Hyogo, Japan
- Blood Type: O
- Height: 159cm
- Specialties: Dance, playng various instruments, back bridge
- Hobbies: Making sweets, singing songs, collecting cute shoes
- Looks Up To: Suzuki Airi, Ikuta Erina
- Hello! Project groups:
Eguchi Saya first appeared as a member of Hello Pro Kenshuusei on March 6, 2017 in an announcement on the official website, alongside Shimakura Rika, Hibi Marina, Doi Rena, Okamura Minami, Matsunaga Riai, Yamada Ichigo, and Nakayama Natsume. She made her first live appearance and was formally introduced at the "Hello Pro Kenshuusei Happyoukai 2017 3gatsu ~Marching!~" event on March 11, 2017.
On June 9, 2018 during the "Hello! Project Kenshuusei Happyoukai 2018 6gatsu ~Niji~" event in Tokyo, it was announced that Eguchi would join the upcoming group featuring previously announced leader Ichioka Reina, along with Nishida Shiori and Shimakura Rika. The group would be unveiled at a later date in 2018.
- [2020.08.07] BEYOOOOONDS① (Ichioka Reina, Shimakura Rika, Nishida Shiori, Eguchi Saya, Takase Kurumi, Maeda Kokoro, Yamazaki Yuhane, Okamura Minami, Kiyono Momohime, Hirai Miyo, Kobayashi Honoka, Satoyoshi Utano)
- [2021.08.07] BEYOOOOONDS②
- TV Programs
-  Hello Pro no Oshigoto Challenge! (ハロプロのお仕事チャレンジ!)
-  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)
-  Kagome GO! ME. "ONE DAY"
-  Attack No.1 (アタックNo.1)
-  Fushigi no Kuni no Alice Tachi (不思議の国のアリスたち)
-  Reborn ~13-nin no Tamashi wa Kami-sama no Yume wo Miru~ (リボーン~13人の魂は神様の夢を見る~) (as stork)
-  Arabeyooooonds Nights (アラビヨーンズナイト) (as Alibaba)
- [2019–] Kanazawa Tomoko no Vivid Midnight (金澤朋子のVivid Midnight)
- [2019–] J3 Tuesday~Midnight IQ~ Madamada Kayoubi~yonds! BEYOOOOONDS QUEST! (J3 Tuesday～Midnight IQ～ まだまだ火曜日よんっ！BEYOOOOONDS QUEST!) (Corner)
- [2020–] BEYOOOOONDS no Biyo～～～～～tto Tobikoe Night! (BEYOOOOONDSのビヨ～～～～～っと飛び越えナイト!)
- [2020–] BEYOOOOONDS no O no Kazu wa Itsutsu Desu (BEYOOOOONDSのOの数は5つです)
- Her favorite genres of music are J-Pop and western music.
- Favorite sports are tennis and soccer.
- Favorite foods are macaroons, mont blanc, buri and hamachi.
- Her motto is "Hard work opens all doors" (努力は全ての扉を開く).
- Thinks her charm point is her long curled eyelashes.
- Her favorite school subject is physical education.
- Her favorite color is dark pink.
- She can dance the samba.
- Shares a birthday with Hello! Project and ANGERME Leader, Wada Ayaka.
- Her favorite Hello! Project song is "The Vision" by Morning Musume.