Inaba collaborated with Slash on the latter's 2009 single "Sahara", and with Stevie Salas on the albums Chubby Groove (2017) and Maximum Huavo (2020).

Koshi Inaba was born and raised in Tsuyama, Okayama, and enrolled in Yokohama National University's Faculty for Education in 1983 to become a qualified mathematics teacher.

[1] Inaba made his musical debut in 1985 whilst still a student, contributing vocals to Toshiya "Ran" Matsukawa's album Burning ~Dedication to Randy Rhoads~ under the stage name Mr. Crazy Tiger.

Beginning with B'z in 1988, Inaba has, together with guitarist Tak Matsumoto, continued to release new material and tour as part of B'z almost every year since.

Inaba has also sung on other artists' releases, such as the Steve Vai song "Asian Sky" from the album The Ultra Zone in 1999.