Hiro Yamamoto was a founding bassist of Soundgarden from 1985 – 1989 when he left the band to finish his Master’s dergree in Physical Chemistry at Western Washington University. Here’s a photo of Yamamoto with Soundgarden.
His last show with Soundgarden was in the Melkweg, Amsterdam after which they got into an argument and Yamamoto subsequently left. He was replaced temporarily by Jason Everman who had played with Nirvana and then permanently replaced by Ben Shepherd in 1991. Here’s a recent photo of Yamamoto at a Sub Pop party with former band mates Kim Thayil and Matt Cameron sans Chris Cornell.
In 1991, Yamamoto formed a three-piece indie band, Truly they released two studio albums and a compilation of unreleased material before breaking up in 2000.