T-Square formed in Tokyo in 1978 under the name The Square. Their classic, most successful lineup — guitarist Masahiro Andoh, bassist Mitsuru Sutoh, saxophonist/flutist/EWI player Takeshi Itoh, keyboardist Hirotaka Izumi, and drummer Hiroyuki Noritake — built a catalog through the late 1970s and 1980s that made them, alongside Casiopea, one of the two or three bands most responsible for defining Japanese jazz-fusion's commercial peak.

In 1988, ahead of a performance at the Roxy Theatre in Los Angeles, the band discovered an unrelated American act already called The Squares and changed their own name to T-Square, a transition fully carried through their catalog by the 1989 album Wave.

Their signature song, "Truth" (1987), became genuinely embedded in Japanese mainstream culture in a way few jazz-fusion instrumentals manage: it served as the official theme for Japan's Formula One broadcasts from 1989 to 2000, followed by a rearrangement, "Truth 21c," in 2001-2002, with further remixes carrying the association through 2006 — nearly two decades of a fusion instrumental as the sound of motorsport on Japanese television. Other well-known songs include "Japanese Soul Brothers," "Takarajima," and "Omens of Love."

A claim tied to their earlier, pre-rename catalog is worth stating with appropriate caution: Discogs's own artist profile for the band states that "Sister Marian," from their Square era, directly inspired the overworld theme of the original Super Mario Bros., composed by Koji Kondo — a claim the Discogs entry links directly to Kondo's own artist page. This is a genuinely notable piece of video-game-music trivia if it holds up, but it was not independently corroborated by a second source during this research.

What is directly confirmed on record: in 2004, T-Square and Casiopea performed a joint concert, released as Casiopea vs The Square Live — the two defining bands of an entire genre sharing a stage.

T-Square's sound bridges American jazz-fusion (Weather Report and Chick Corea's Return to Forever are commonly cited touchstones for this generation of Japanese fusion bands) with a melodic, radio-friendly songcraft that helped carry instrumental fusion into Japanese mainstream broadcasting via "Truth" and its F1 association.