In 2000, Mika made her stage debut as Janet in the Japanese version of the musical Annie. She also had small roles in Battle Royale II: Requiem and Suicide Circle before landing the role of Koume "Umeko" Koudo/DekaPink in 2004's iteration of the Super Sentai franchise, Tokusou Sentai Dekaranger.

Mika then diversified into voice acting in 2005, voicing the character Mokona in the anime Tsubasa Chronicle and xxxHoLiC, based on Clamp's popular mangas. She has also presented a children's variety show Nyanchuu World on the NHK channel, as well as net radio work for Tsubasa Chronicle (with fellow seiyū Yui Makino) and Mai Otome (with Ami Koshimizu), the popular anime in which she plays the lead character Arika Yumemiya. On December 16, 2009, her birthday, she married actor Yūji Kishi, who is 13 years her senior. They met during the 2007 Japanese stage tour of Les Miserables, and coincidentally both have had their acting debuts in a Super Sentai Series.

Mika then diversified into voice acting in 2005, voicing the character Mokona in the anime Tsubasa Chronicle and xxxHoLiC, based on Clamp's popular mangas. She has also presented a children's variety show Nyanchuu World on the NHK channel, as well as net radio work for Tsubasa Chronicle (with fellow seiyū Yui Makino) and Mai Otome (with Ami Koshimizu), the popular anime in which she plays the lead character Arika Yumemiya. On December 16, 2009, her birthday, she married actor Yūji Kishi, who is 13 years her senior. They met during the 2007 Japanese stage tour of Les Miserables, and coincidentally both have had their acting debuts in a Super Sentai Series.