Kazumasa Akiyama (秋山一将) was born on 17 January 1955 in Asakusa, Tokyo. By his own account, relayed on a long-running fan blog, he taught himself guitar from the age of ten, starting from the Beatles and Ray Charles before jazz took over. He was playing professionally while still in high school, and he went on to work in the groups of three of Tokyo fusion's busiest bandleaders: the bassist and cellist Isao Suzuki, the pianist Mikio Masuda and the saxophonist Yasuaki Shimizu.

His first recorded credit came on 19 and 27 October 1976, when he was 21. At Epicurus Studio in Tokyo the Isao Suzuki Sextet cut Ako's Dream for Three Blind Mice, with Suzuki on cello, Kazumi Watanabe and Akiyama as the two guitarists, Tsuyoshi Yamamoto on keyboards, Motohiko Hamase on bass and Akira Doi on drums. Six months later, on 13 April 1977, he was one of two electric guitarists, again alongside Watanabe, on Suzuki's Cadillac Woman at Onkio Haus in Tokyo. The rhythm section on that Flying Disk date was American: Cedar Walton on piano and electric piano, Sam Jones on bass and Billy Higgins on drums. Akiyama was 22. His name is also in the credits of the same year's Jazz of Japan: Live Under the Sky '77, the double album recorded at the Denen Colosseum festival in Tokyo on 24 July 1977, and of Tomas Band's Vol. 1 and Some Feeling by the singer Minami Yasuda (安田南), a Frasco album arranged by Naoya Matsuoka. In December 1977 he played electric guitar and sang on Masuda's Moon Stone, recorded at Nippon Columbia's first studio with Watanabe, Hamase and the drummer Hideo Yamaki.

In 1978 he made his own record. Dig My Style (Flying Dog FLD-10010) is eight tracks of mellow, soul-tinged fusion, with Akiyama singing in English and playing guitar over a band that reference works name as Masanori Sasaji on keyboards, Shimizu on tenor saxophone and Yamaki on drums. Sasaji, Shimizu and Yamaki went on to form the group Mariah, whose 1979 debut album also carries Akiyama's electric guitar. A Victor reissue series brought Dig My Style back on CD in July 2016, and Tower Records and Victor issued it as an SACD on 13 March 2024 as part of the ADLIB Best Record SACD Collection.

The same autumn he took part in a project that became the other pillar of his name. On 20 and 21 October 1978 at Pit Inn in Roppongi, Akiyama, Kenji Omura, Katsutoshi Morizono and Jun Yamagishi played the live sets issued on 30 December as Guitar Work Shop Vol. 2 Live, with Ryuichi Sakamoto among the keyboard players behind them. In November CBS/Sony released New York, a showcase on which eight guitarists each arranged one piece; Akiyama's was his own composition, "Central Park", and the others on the record include Masaki Matsubara and Tsunehide Matsuki. The 1983 compilation Off Shore collected "Central Park" with other pieces from that record.

Beyond the Door followed in 1979, billed to Akiyama with Next Page, the band he had formed with Sasaji. Hamase played bass, Doi drums, and the singers Noriko Miyamoto and Jimmy Murakawa sang chorus. It was reissued on CD for the first time on 21 September 2016. A second Guitar Workshop volume was cut direct to disc on 29 September and 3 October 1979 and released by Invitation in 1980; Akiyama's contribution, "Hawaiian Village", is a piece for acoustic guitar that he wrote himself.

The 1980s were mostly a sideman decade, and a busy one. His guitar is on Noriko Miyamoto's Push (1978, produced by Suzuki) and Vivid (1979), on Yasuko Agawa's Journey (1980), recorded between 8 September and 3 October 1980, on Yamamoto's Ma Mémoire (Warner, 1981) and on Naomi Akimoto's The 20th Anniversary (1982). In 1982 he was one of the five names on the cover of Zoomin' (Better Days), led by the drummer Motohiko Hino and the bassist Nobuyoshi Ino with Naoki Kitajima on keyboards and Kenji Nishiyama. He played on Jun Miyake's June Night Love (1983), on the drummer Tatsuya Nakamura's Locus (1984) and on three albums by the bassist Yoshio Suzuki: Touch of Rain (1985), Fairy Tale (recorded 29 and 30 January 1987) and Alone in the Pacific (recorded in August 1989). In 1989 he was the guitarist on Hiromasa Suzuki's Cleopatra D.C., with Hidefumi Toki on saxophone.

The 1990s belong to the saxophonist Kohsuke Mine. Akiyama was the guitarist in Mine's quintet with the pianist Junichiro Ohkuchi, the bassist Tsutomu Okada and the drummer Ryojiro Furusawa, and the group recorded three albums for the Verve and Media Rings labels: Major to Minor (recorded at the Tokyo club Body & Soul in April and August 1993, released on 26 November 1993), In a Maze (25 June 1995) and Balancez (25 October 1997). In 1998 he was in the band behind Chie Ayado on her first album, For All We Know, with Hino, Yoshio Suzuki, Okada and Masuda.

His own name returned in 2008 with Dr. Rain (Aketa's Disk, released 25 May 2008), on which he plays guitar and sings, with the drummer Tamaya Honda, the organist Takeshi Shibuya, the saxophonists Nao Takeuchi and Mine, and a second guitarist, Akihiro Ishiwatari. Four years earlier, on 29 and 30 October 2004, Akiyama and Mine had played the live sets at Jazz Inn Lovely that were issued under the title Quiet Storm. He has gone on leading his own quartet in club dates, including at the Shizuoka venue Lifetime, and his Victor-era fusion records have kept turning up on reissues and compilations, among them the 2025 Light Mellow Deluxe set of Yasuko Agawa's recordings.

Akiyama is a guitarist whose public identity splits cleanly in two. As a leader in 1978 and 1979 he made the sweet end of Japanese fusion: English-language vocals, a rounded guitar touch with delicate, bluesy phrasing, and arrangements by the keyboardist Masanori Sasaji that sit nearer to what later became known as AOR than to the harder electric jazz of his Guitar Work Shop colleagues. Reviewers have compared the unforced vocal to Michael Franks and the lead playing, in places, to George Benson.

As a sideman he is a different player. On Isao Suzuki's records he is one of two electric guitars in a band that also holds Cedar Walton and Billy Higgins; in Kohsuke Mine's quintet through the 1990s he plays straight-ahead jazz in a working group; and in the studio he moved between fusion, city-pop sessions for Noriko Miyamoto and Naomi Akimoto, and the arrangement-heavy pop-jazz of Yasuko Agawa's Journey. What ties those settings together is the same unhurried lead voice, and a habit of writing a melodic piece of his own ("Central Park", "Hawaiian Village") when a project gave each guitarist one slot.