Tomatsu is known for voicing main heroines as Asuna Yuuki in Sword Art Online, Saki Rukino in Valvrave the Liberator, Zero Two in Darling in the Franxx, Lala Satalin Deviluke in To LOVE-Ru, Kyoko Hori in Horimiya, Morgiana in Magi: The Labyrinth of Magic, 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 Kannagi: Crazy Shrine Maidens.

In 2009, she became part of the music unit Sphere, alongside Aki Toyosaki, Minako Kotobuki and Ayahi Takagaki.

[6] Tomatsu made her voice acting debut in 2007, playing a student in Gakuen Utopia Manabi Straight!.

[8] That same year, she played the roles of Shiho Sannomiya in Zettai Karen Children,[9] Lala Satalin Deviluke in To Love-Ru,[10] and Nagi in Kannagi: Crazy Shrine Maidens.

Tomatsu performed the song "Sekai de Ichiban Yabai Koi" (世界で一番ヤバイ恋), which was used as the fourth ending theme for the series Kyōran Kazoku Nikki.

), was used as the opening theme to the anime television series Kannagi: Crazy Shrine Maidens; the single was released on October 28, 2009.

[20] Her third single "Musuhi no Toki" (産巣日の時) was released on November 26, 2008; the title track is used as the ending theme to Kannagi: Crazy Shrine Maidens.

[22] Her fourth single "Koi no Uta" (こいのうた) was released on May 13, 2009; the title track is used as the ending to the anime series Shinkyoku Sōkai Polyphonica S.[23] 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.

"Dream World") 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.

[34] 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.

[42] Her eighteenth single, "Uchōten Traveller" (有頂天トラベラー), was released on October 23, 2017; the title track is used as the ending theme to the anime series PriPri Chi-chan!!.