Ishimaru played various instruments, such as the piano, cello, trombone, and snare drum, since childhood.
[2] In 1990, he debuted in the role of Raoul of Shiki Theatre Company's The Phantom of the Opera.
[2] Among other activities, he appeared in advertisements for Oronamin C (co-starring with SMAP's Takuya Kimura)[2] and Nescafé Gold Blend.
In 2013, he played branch manager Tadasu Asano in the Tokyo Broadcasting System television drama Hanzawa Naoki.
[2] On 2 April 2017, he was named the sixth chairperson of TV Asahi's long-running music programme Daimei no nai Ongakukai.