Toshihiro Akamatsu (赤松敏弘) was born in Matsuyama, in Ehime Prefecture on the island of Shikoku, on January 4, 1957. By his own account he started on piano at three, fell for jazz at eleven and began teaching himself the vibraphone at thirteen. As a primary school pupil he had seen Gary Burton on television without knowing his name or what the instrument with the glittering keys was called. At sixteen he began private lessons with the marimba pioneer Keiko Abe, and he started playing jazz in earnest while a student in the music department of Sakuyo High School in Okayama. After university, where he was already working local live houses and television, he moved to Tokyo in 1980 and formed his own group.

The first turning point was a competition. At ANNEX 82 in 1982 he took the Best Player Prize, the Judges Special Prize and the Guest Judge Prize, the last awarded by the keyboardist George Duke. The second came in 1985, when Burton visited Japan for a Berklee in Tokyo event and recognised his talent. The following year Akamatsu entered the Berklee College of Music in Boston on a scholarship, majoring in vibraphone and composition. He won the Gary Burton Award and a Professional Scholarship, according to his biography played with fellow students including the pianist Makoto Ozone, and graduated in 1989 near the top of the jazz composition division (his own biography places him second).

Back in Japan he became a regular on the NHK-FM programme Session and, according to his own biography, joined groups led by the pianist Hideo Ichikawa, the bassist Yoshio Suzuki and the trumpeter Terumasa Hino, the last in 1994. He also became a busy studio player outside jazz. Discogs credits him on vibraphone for the Tokyo rock-pop band Original Love (on Love! Love! & Love!, 1991, and Odoru Taiyo, 2003), the singer Bird (Double Chance, 2003, and Bird's Nest, 2005), Kyoko Fujimoto (1992) and the group Melange (1995); his own biography adds Yuichi Otsuka, Marcato, Masayuki Suzuki and Toshiki Kadomatsu.

His first record under his own name, Les Enfants III featuring Toshihiro Akamatsu (Polydor, November 1, 1990), was a vibraphone album of soul and pop standards with a large cast of guests. In 1991 his group A-Project and a duet with the guitarist Kazuhiko Michishita appeared on the BMG Funhouse compilation Now's the Time Workshop Vol. 2. In 1999 he formed a band called The Next Door, tied to young players and a regular at Roppongi Pit Inn and the Yokohama Jazz Promenade, and its first album, Next Door - Birth of the "Swift Jazz" (VEGA Music Entertainment, 2000), had been preceded by a download-only mini-album, Londonderry Air, recorded in December 1999.

The recordings that made his name came from the Three Blind Mice label. Six Intentions (TBM, 2002), a set of six different small-group concepts recorded at Crescente Studio in Tokyo in April 2002 and issued on JVC's high-fidelity XRCD24 format, brought in the pianist Hideo Ichikawa and Yoshio Suzuki as guests; Suzuki wrote "Mistral" for it and Ichikawa the opener "Reminiscence". Its follow-up, Still On The Air (TBM, 2003), added the veteran guitarist Sadanori Nakamure and was nominated for the Japan Jazz Prize at the 37th Swing Journal Jazz Disc Awards.

From 2005 he recorded for VEGA Music Entertainment: Synergy and Focus Lights (both 2005), Tide Graph (2007, built from three kinds of duo), the expanded Six Intentions - Complete Edition (December 2007), Stream of Life (2008), Axis (2010, with his Akamatsu The NewQuartet), and then a long partnership with the pianist Hakuei Kim, the trumpeter Hikari Ichihara and the drummer Taro Koyama on Majestic Colors (2014, his fourteenth album by his own count), Synonym (2017, his fifteenth) and Next Door - New Life (2020, his sixteenth). Synonym was named an Amazon's Choice in vibraphone products for two years from July 2018. In 2007 he published a repertoire book for jazz marimba and vibraphone through Yamaha Music Media, and in 2020 an e-book memoir of his thirty years as a working vibraphonist.

In November 2023, after twenty years with VEGA, he started his own label, AMS Record, and released My Real Book - Season 1 & 2, billed as his seventeenth album. It pairs two groups on one disc: the regular quartet with Kim, Ichihara, the bassist and cellist Takashi Sugawa and Koyama, and a second session with the young pianist Shinichiro Mochizuki. Jazz Life, Jaz.in and Jazz Hihyo all reviewed it, and it appeared in Jaz.in's critics' best-albums features for 2023. From April 2024 he also hosted a weekly jazz programme, Gloaming "E", on FM Ehime, broadcast nationwide on radiko, and in 2024 he played the Yokohama Jazz Promenade in October and led a Shinjuku Pit Inn date in August that he described as his first Pit Inn appearance in twenty years.

Toshihiro Akamatsu passed away on October 7, 2025, at his home in Tokyo. He was 68. The Ehime Shimbun and Jaz.in both reported his death, and FM Ehime announced it on its official account.

Akamatsu played with four mallets, the technique he first watched Gary Burton use on television, and later studied the vibraphone with Burton himself, while his early marimba training with Keiko Abe gave him a second voice on the instrument. He recorded marimba on several albums and often played in duo with marimba or piano partners, including Yuki Arimasa on Synergy and Tide Graph and Miki Matsushima on marimba.

His own writing and the standards he chose sit squarely in post-bop and mainstream jazz: Wayne Shorter's "E.S.P.," Cedar Walton's "Bolivia," Eric Dolphy's "The Prophet," Chick Corea's "Return to Forever" and Jaco Pastorius's "Havona" all turn up on his records alongside originals. In a 2023 interview he described improvisation as the reason he loved jazz, and said he wanted to explore its essence and its diversity. A few early items, such as the 1999 and 2000 Next Door material, lean toward smooth jazz and fusion textures; the later records are acoustic and group-interactive, and the Jazz Life reviewer of My Real Book compared its small-ensemble writing to chamber music.

Outside the leader records he moved comfortably between worlds: Original Love's jazz-tinged pop, the vocalist Bird's soul-jazz, and younger players whose albums he produced, including the vibraphonist Hitoshi Nakajima (Pioggia, 2018), the marimba player Miki Matsushima and the vibraphonist Yukari.