Sachi Hayasaka (早坂紗知) was born in Tokyo on 26 February 1960, the same day as the pianist Yosuke Yamashita, who was born on 26 February 1942, and the coincidence ended up organising a large part of her career. She started piano lessons at five, took up the alto saxophone in her school wind band as a teenager, and went on to study jazz and classical saxophone at Tamagawa University. She took lessons from the saxophonist Hidefumi Toki, and as a young player she worked part-time in Tokyo jazz kissa, among them Peter-Cat, the club run by the novelist Haruki Murakami, and she has a long association with the kissa Paper Moon.

She is described on her own label's Bandcamp page as one of Japan's first female saxophonists. Early outings included a sunrise concert on the summit of Mount Fuji in 1985, organised by the drummer Mitsumasa Nonaka, and playing in Yosuke Yamashita's Panja orchestra, an association that has lasted decades. In 1987 the German guitarist Hans Reichel invited her on a tour of western Europe. She also spent roughly twenty years in the band of the actor and singer Yoshio Harada.

Her debut album Free Fight was recorded in Tokyo in November 1987 and January 1988 and issued on Teruto Soejima's small Mobys label as Sachi Hayasaka & Stir Up!, with Toshiki Nagata on bass, Ken Tsunoda on drums, Naoki Kubojima on piano, Tomohiro Yahiro on percussion, Keiki Midorikawa on cello and Tetsuji Yoshida on trumpet. It mixed free jazz, post-bop and heavy groove, and it is the record BBE Music chose in February 2026 as the 20th release in its J Jazz Masterclass reissue series, remastered from tapes Hayasaka supplied and accompanied by her own account of her life in jazz.

In the late 1980s she moved to New York for several years, working with the drummer Pheeroan akLaff and the pianist Cliff Korman, and kept returning to the city afterwards. The second Stir Up! album, Straight to the Core (Three Blind Mice, 1989), was cut in Tokyo on 5 and 6 November 1989, with two tracks added at Baby Monster Studio in New York on 25 November, where the trumpeter Wadada Leo Smith appears as a guest according to the album's retail listing. The Jazz.com encyclopedia names Smith, with Yamashita, as her avant-garde mentors.

The band's best-known night is the annual "2.26" concert, long held at Buddy in Ekoda, Tokyo, on 26 February to mark the shared birthday of Hayasaka, Tsunoda and Yamashita. The 1992 concert was recorded and released by the German label Enja as 2.26 (1994), with Yamashita guesting on piano and Tatsuya Sato on tenor saxophone. The event has since produced a series of live albums, among them Black Out! (Live at Buddy / 1999 2.26), 2.26 Birthday Live 30th Anniversary (2016) and a 2020 set with Yamashita and the drummer Takeo Moriyama, and the 40th edition fell on 26 February 2026.

Through the 1990s she recorded Milagros (Off Note, 1996) and Double Rainbow (1998), the latter cut in Brooklyn on 31 October and 1 November 1998 with Pheeroan akLaff, the pianist Febian Reza Pane and the violinist Shiro Sadamura, and issued as the first release on her own Nbagi Record label. In April 1998 she was a front-line member of Satoko Fujii's sextet on Past Life, with Natsuki Tamura on trumpet, and that November she played soprano saxophone on three tracks of Fujii's Brooklyn trio session Kitsune-bi, released by John Zorn's Tzadik label. In May 1998 she also formed Black Out, a saxophone quartet, which recorded as Sachi Hayasaka's Dynamite Saxophone Quartet (2001).

In June 2002 she founded Minga, a percussion-driven world-jazz group with Nagata, the percussionists Tomohiro Yahiro and Gen Ogimi and the Senegalese sabar drummer Wagane Ndiaye Rose. Its album Minga, recorded at Gok Sound in Tokyo on 18 to 20 November 2002, came out in 2003 on Tzadik (TZ 7244) with John Zorn as executive producer. Around it came Beat Beat Jazz Beat! (2005) and Samgha (2006, Ohrai Records) with Pheeroan akLaff, and East Village Tales (2009), a live document of a New York special unit recorded at Local 269, The Stone and No Trunks in September and October 2009.

Since 2012 her main vehicle has been TReS, a family trio of Hayasaka, her husband Toshiki Nagata on bass and their son RIO on baritone saxophone, formed for a performance in Buenos Aires. TReS has toured Brazil and Argentina and played festivals in Buenos Aires, Seattle and Cuba, and its albums run from Escualo (Dedicado a Astor Piazzolla) (2013) to the larger Baila TReS and Dos Familias+ lines with pianist Shiko Ito and percussionists Gen Ohmigata and Umi Ohmigata, whose Pit Inn recordings from September 2024 came out in 2025 as Nue and Desertification. On 21 and 22 November 2026 TReS is booked into the Barbican Hall, London, for "Haruki Murakami's Jazz at Peter Cat" at the EFG London Jazz Festival, on a bill that also lists the Junko Onishi Trio and The Blend, the group of the bassist Yoshio Suzuki, who passed away on 23 September 2026. She is alive and active.

Hayasaka's sound is a hard, bright alto and soprano built on the Ornette Coleman, Roland Kirk and David Murray line, and she has named all three as influences. The earliest records, Free Fight and Straight to the Core, sit in a free-leaning post-bop idiom, with several brief pieces of under two minutes (the title track of Free Fight runs one minute and forty-five seconds) set between long ones such as the eleven-minute "Monster's Teardrops". The live birthday records with Yamashita stretch out further, with tracks of ten to eighteen minutes on the 1999, 2016 and 2020 sets.

Two other strands run alongside the free playing. One is a taste for tunes with a plain melodic spine: she plays Tom Waits' "Take Care of All My Children" on 2.26 and "You Don't Know What Love Is" on Milagros, her saxophone quartet album includes "Viva Ornette!" and Piazzolla's "Libertango", and TReS devoted a whole album to Piazzolla. The other is rhythm from outside jazz: the Senegalese sabar drumming of Wagane Ndiaye Rose on Minga and Beat Beat Jazz Beat!, and the Latin-leaning Baila TReS records, which is why Latin Jazz sits beside the free-jazz tags.

She is also a bandleader by temperament. She produced most of her own records, released them on her own Nbagi Record label from Double Rainbow (N-001) onward, and built each band (Stir Up!, Black Out, Minga, TReS) around a shifting circle of long-term collaborators, with the bassist Toshiki Nagata as the constant.