Kei Akagi (ケイ赤城, real name 赤城恵) was born in Sendai on March 16, 1953, and his career runs on two shores. His family lived in Cleveland, Ohio, from his early childhood until he was 12, and he started piano at five, studying piano theory and music history at the Cleveland Music Settlement. Back in Japan he first met jazz as a high school student in Aomori Prefecture, then studied philosophy and composition at International Christian University. In 1975, at 22, he returned to the United States for a doctoral program in philosophy at the University of California, Santa Barbara.

Jazz won out over the academic path. At Santa Barbara he wrote and orchestrated for the university jazz band and played piano in pickup bands for Blue Mitchell and Art Pepper, and at 25 he gave up the route toward a professorship. In 1979 he became the pianist in the group led by Airto Moreira and Flora Purim and stayed with it for seven years. His keyboards are credited on Airto's Latino / Aqui Se Puede (1984), on Three-Way Mirror (1985, billed to Airto, Purim and the saxophonist Joe Farrell) and on Purim's Midnight Sun (1988). Along the way he played on Gary Lefebvre's quartet records, on the guitarist Frank Gambale's first albums, and on Kazumi Watanabe's Mobo (1984), cut in New York with Marcus Miller and a rotation of drummers. From 1986 to 1988 he worked in the Al Di Meola group, keyboards and arrangements on Tirami Su (1987).

Japan stayed in his catalogue even in these years. In 1983 Nippon Columbia issued Symphonic Fusion: The Earth, an album of music he composed and arranged for a Japanese television program, which is the first record under his own name.

In 1989 he joined Miles Davis. The route in was an audition tape: Di Meola's road manager knew Davis's road manager, Gordon Meltzer, and Meltzer asked Akagi to send one. By the dating in George Cole's book on Davis's last decade, The Last Miles, he played in the band from March 1989 to November 1990, while his own biography gives 1989 to 1991. He is credited on the soundtrack Dingo (1991, with Michel Legrand), on the concert film Miles in Paris and on the live album Live Around the World (1996), and Japanese press notices have billed him as the first Japanese musician to be a regular member of a Davis band. Cole reports that he left because he was hearing ideas that the band's tightly arranged music left no room for. He later made a tribute album of his own, New Smiles and Traveled Miles (Groove Note, 2000), recorded in 1998 as a trio with the bassist Darek Oleszkiewicz and the drummer Joe LaBarbera.

After Davis he joined the band of Stanley Turrentine and stayed about ten years. He is the pianist on the live Live! At Blues Alley (recorded November 30, 1991) and on Turrentine's Do You Have Any Sugar? (Concord Vista, 1999). His own records from this period are a run of acoustic post-bop dates for American labels. Playroom (Moo, 1992) features Rick Margitza on saxophone with John Patitucci and Bob Harrison alternating on bass. Sound Circle (1992), billed to the Asian American Jazz Trio, is a trio with Rufus Reid and the drummer Akira Tana, recorded December 16 and 17, 1991. Mirror Puzzle (AudioQuest, 1994) was recorded in Hollywood on May 7 and 8, 1994, in a quartet with Margitza, the bassist Charles Fambrough and Willie Jones III. The same producer and engineer recorded him on James Newton's Suite for Frida Kahlo (1994).

The Japanese side of his working life took a regular shape in the late 1990s. His own biography says he has toured Japan every year since 1998 with a group of Japanese musicians, and in 2000, on a trip to Japan, his producer introduced him to the bassist Tomokazu Sugimoto and the drummer Tamaya Honda, the son of the pianist Takehiro Honda. That Tokyo trio made A Hint of You (2003) and Modern Ivory (2004) for the One Voice label and a live set, and it recorded Liquid Blue for Time & Style in 2007. Palette (One Voice, recorded in March 2001 at Sony Music Studios, Tokyo) is the first of these: part trio with Sugimoto and Honda, part trio with the bassist Nobuyoshi Ino and the drummer Hiroshi Murakami, and on several tracks a quartet with Kohsuke Mine on tenor saxophone and bass clarinet. In 2002 he recorded a two-piano set with the Japanese pianist Fumio Karashima, issued as Grand New Touch.

Since 2007 his leader records have gone out on Tokyo's Time & Style label: after Liquid Blue came Circlepoint (2014), Contrast & Form (2016) and Aqua Puzzle (2018), then the companion albums Backfloating and Midnight Sidewalk, released together with a trio of Akagi, the bassist Shunya Wakai and the drummer Sota Kira, which the label describes as its fifth collaboration with him. In the United States he taught at the University of California, Irvine from the mid-1990s, as Chancellor Professor of Music and director of jazz studies, until his retirement in 2023, and he is now Professor Emeritus there. He has more than 100 compositions in print, has recorded 14 albums as a leader and appears on more than 60 as a sideman. His own biography also lists Freddie Hubbard, Ron Carter, Charlie Haden, Sadao Watanabe and Jean-Luc Ponty among the musicians he has worked with.

Akagi plays modern acoustic piano jazz in the post-bop and hard bop tradition. A reviewer who heard his Tokyo trio in 2007 described it as hard bop with a touch of free and avant-garde playing, fast in tempo and demanding on the listener's sense of rhythm, and placed him in the line of keyboardists that includes Herbie Hancock and Chick Corea. Discogs tags the Asian American Jazz Trio record Sound Circle as post-bop and modal, and the trio's repertoire there includes Wayne Shorter's "Nefertiti" and "E.S.P.".

The electric side of his playing comes from his early professional years. In the Airto and Purim band and in Al Di Meola's group he worked on keyboards and synthesizers in Brazilian-jazz and fusion settings, and on Di Meola's Tirami Su he also wrote arrangements. With Davis he was again a keyboardist, and he has said the main thing he took from Davis was that music is far larger than whatever is being played at any given moment.

His tribute album New Smiles and Traveled Miles reads the Davis book directly, with "Milestones" in both its 1947 and 1955 forms, "Love for Sale," "Stella by Starlight" and "Mr. Pastorius," plus originals in the same trio format. His Tokyo trio albums mix his own compositions with standards: Palette includes "Lazy Bird" and "You Don't Know What Love Is," A Hint of You has "Don't Explain" and "Stablemates," and Modern Ivory takes up "Dolphin Dance" and "Well, You Needn't." More than 100 of his compositions are published through his own Red Castle Music.