is a Japanese actress and singer, employed by MusicRay'n. She received the Rookie of the Year award at the 3rd Seiyu Awards and the Synergy Award at the 9th Seiyu Awards. Tomatsu is known for voicing main heroines as Asuna Yuuki in Sword Art Online, Haru Okumura in Persona 5, Zero Two in Darling in the Franxx, Lala Satalin Deviluke in To LOVE-Ru, Kyoko Hori in Horimiya, Morgiana in ', Eleonora Viltaria in Lord Marksman and Vanadis and Naruko "Anaru" Anjo in Anohana.
Tomatsu began a singing career in 2008, performing the song "Naissance" which was used as the ending theme to the television drama series Here Is Greenwood. Her second single "Motto Hade ni Ne" was used as the opening theme to '. In 2009, she became part of the music unit Sphere, alongside Aki Toyosaki, Minako Kotobuki and Ayahi Takagaki. She released her first album Rainbow Road in 2010, and two compilation albums in 2016.
Tomatsu was born in Ichinomiya, Aichi. Her voice acting career began when she participated in an audition held by Sony Music Entertainment Japan subsidiary Music Ray'n from 2005 to 2006. In January 2006, she participated in the Tà Âhà  Cinderella audition held by Tà Âhà  Entertainment.
Tomatsu made her voice acting debut in 2007, playing a student in Gakuen Utopia Manabi Straight!. That same year, she played her first starring role as Corticarte Apa Lagranges in Shinkyoku SÃ Âkai Polyphonica.
After graduating from high school, Tomatsu moved to Tokyo in 2008 to go to university and to continue her voice acting career. That same year, she played the roles of Shiho Sannomiya in Zettai Karen Children, Lala Satalin Deviluke in To Love-Ru, and Nagi in '. She then made her live-action debut as Mieko Nitta in the drama series Here Is Greenwood. She also played the role of Ami Misaki in the television drama series RH Plus. She received the Rookie of the Year Award at the 3rd Seiyu Awards.
In 2012, Tomatsu played Asuna Yuuki in Sword Art Online. In 2013, she received the Best Supporting Actress Award at the 7th Seiyu Awards, and the Synergy Award for her role in Yo-Kai Watch at the 9th Seiyu Awards. In 2018, she appeared as herself in the television drama series Koe Girl!, which featured her as a voice actress taking care of the series' main characters; the series also featured footage from one of her concerts. She also played Zero Two in Darling in the Franxx. In 2021 she played Kyoko Hori in Hori-san to Miyamura-kun.
Tomatsu performed the song , which was used as the fourth ending theme for the series Kyà Âran Kazoku Nikki. Her next release was the song "Naissance", which was used as the ending theme to the drama series Here Is Greenwood. "Naissance", her first single, was released on September 3, 2008. Her second single and first anime-related single, , was used as the opening theme to the anime television series Kannagi: Crazy Shrine Maidens; the single was released on October 28, 2009. Her third single was released on November 26, 2008; the title track is used as the ending theme to Kannagi: Crazy Shrine Maidens.
In 2009, Music Ray'n formed the music unit Sphere, which consists of Tomatsu, Aki Toyosaki, Minako Kotobuki and Ayahi Takagaki. Her fourth single was released on May 13, 2009; the title track is used as the ending to the anime series Shinkyoku SÃ Âkai Polyphonica S. This was followed by her fifth single "Girls, Be Ambitious", which was released on February 8, 2010; the title track is used as the ending theme to the anime series Sound of the Sky. She released her first solo album Rainbow Road on February 24, 2010; the album peaked at No. 15 on the Oricon weekly charts and charted for four weeks. She then released her sixth single on August 16, 2010. Her seventh single "Baby Baby Love", used as the ending theme to the 2010 anime television series Motto To Love-Ru, was released on November 3, 2010.
Her eighth single, "Oh My God", was released on July 25, 2011; the title track was used as the anime series Nekogami Yaoyorozu. This was followed by her ninth single which was released on July 25, 2012; the title track was used as the first ending theme to the anime television series Sword Art Online. Her next release was her tenth single which was released on October 29, 2012. Her second solo album Sunny Side Story, released on January 16, 2013, peaked at No. 5 on the Oricon weekly charted and charted for five weeks.
Her eleventh single, "Pachi Pachi Party", was released on July 22, 2013, and her 12th single was released on January 27, 2014. She released her 13th single "Fantastic Soda!!" on August 11, 2014. This was followed by her 14th single "Courage", released on December 3, 2014, and used as the second opening theme to the anime television series Sword Art Online II. It became her best performing single to date, peaking at No. 4 on the Oricon weekly charts and charting for eleven weeks. Her third solo album Harukarisk*Land, released on March 18, 2015, peaked at No. 5 on the Oricon weekly charts and charted for four weeks.
Tomatsu released her fifteenth single "Step A Go! Go!" on October 12, 2015. This was followed by her sixteenth single , which was released on February 29, 2016. She then released two best albums titled and on June 15, 2016. In July 2016, as part of Sphere, she made her North American live debut at Anime Expo. Her seventeenth single was released on November 7, 2016; the song "Two of Us" is used as the theme song to the video game '. Her eighteenth single, , was released on October 23, 2017; the title track is used as the ending theme to the anime series PriPri Chi-chan!!. She released her fourth solo album Colorful Gift on May 14, 2018. Her 18th single "Try & Joy" was released on September 5, 2018. Her 19th single "Resolution" was released digitally on October 13, 2019, and received a physical release on November 20, 2019; the title song is used as the third opening theme to the anime series Sword Art Online: Alicization.
Tomatsu announced her marriage on her blog on January 11, 2019. She gave birth to her first child, a daughter, on February 9, 2021. On May 20, 2025, she gave birth to her second child.