Born in Kōchi, Japan in 1972, Mizuta's interest in music began to grow when he "was in the second or third grade". Although still interested in music, Mizuta studied law and economics at Chiba University. He composed his first song while in his last year there, and after graduating went to work for Capcom in 1995 as a composer. He began his career scoring the Street Fighter series where he was part of the sound team for Street Fighter Alpha in 1995.
In 1998, while still working for Capcom, Mizuta applied to Square as a composer in response to an advertisement and was hired. His first assignment for Square was to score Parasite Eve II, for which he was the sole composer and spent a year and a half working on. The original Parasite Eve game was scored by Yoko Shimomura, and Mizuta incorporated some of the original game's musical themes into the sequel. Mizuta's next role was as the main composer for Final Fantasy XI, with assistance from Nobuo Uematsu and Kumi Tanioka. Mizuta remained with the Final Fantasy XI project for over ten years, serving as the sole composer for the game's five expansions, and considers it his life's work. During this period, Mizuta became involved in The Star Onions, a band composed of Square Enix composers for which he plays bass guitar. Other members of the band, which plays arrangements of songs from Final Fantasy XI, include Tanioka, Hidenori Iwasaki, and Tsuyoshi Sekito. The band has since released two albums, Music from the Other Side of Vana'diel and Sanctuary.
Mizuta has also worked on several other projects for Square Enix, including Blood of Bahamut and Guardian Cross. He has also worked on many other games in the Final Fantasy series, including Final Fantasy: The 4 Heroes of Light, Final Fantasy XIII-2, Final Fantasy XIV, Final Fantasy XIV: A Realm Reborn, and Lightning Returns: Final Fantasy XIII.
For games, Mizuta is primarily focused on creating music that fits the title and the scene at hand, without consideration for how it might sound in isolation. On older consoles, the hardware restricted composers to three channels of audio. Working within these limitations, Mizuta was challenged to create strong, memorable melodies without the aid of atmospheric and accompanying lines. Even without such constraints in modern titles, he feels that this style has its merits and is worth preserving. On the other hand, for alternative presentations of his music such as live performances or piano arrangements, Mizuta feels more free to have fun and play it however he likes. Mizuta is heavily influenced by the work of Ryuichi Sakamoto, as well as Nobuo Uematsu, his superior at Square. He also draws inspiration from a variety of film scores as well as fan remixes of his work on YouTube.