[4] This tour band, Tokyo Jihen, debuted as a fully fledged musical act in 2004 with the single "Gunjō Biyori", which Hiizumi composed.

The band's debut album Kyōiku was released in November 2004, also featuring his songs "Genjitsu ni Oite" and "Service", followed by the Dynamite tour in early 2005.

[5] Hiizumi decided to leave the band after the tour to focus on his work with Pe'z, and announced this on July 1, 2005.

He also worked in the musical collaboration between Pe'z and folk singer Suzumoku, Pe'zmoku, and performed the Bleach ending theme song "Gallop".

Hiizumi collaborated with Pe'z members Masahiro Nirehara and Kou to create the jazz trio H Zettrio in 2013, and released the album Mitsuboshi on December 4, 2013.