Born in Fukuoka, Japan, Shiro Hamaguchi graduated with a music degree from Tokyo University of the Arts, where he befriended fellow video game musician Masashi Hamauzu.

In 1996, he joined the anime and video game music production company Imagine, where he worked alongside famed composers Hayato Matsuo, Kohei Tanaka, and Kow Otani.

[1] Subsequently, he created music for the anime series Ehrgeiz (unrelated to the video game) and AWOL - Absent WithOut Leave.

These pieces and nine new arrangements appeared in the orchestral album Fithos Lusec Wecos Vinosec Final Fantasy VIII.

[1] In 2000, Hamaguchi composed the Megumi no Daigo film and the Dinozaurs anime series, the latter with Imagine colleague Akifumi Tada.

[10] He also made new arrangements of "Opening ~ Bombing Mission", "To Zanarkand", "Ronfaure", "You're Not Alone", and "Opera 'Maria and Draco'" for the concert series Tour de Japon: Music from Final Fantasy in 2004.

[12] A handful of Hamaguchi's orchestral arrangements were added to Tour de Japon's American successor Dear Friends - Music from Final Fantasy, which made its debut in May 2004 in Los Angeles.

[14] The same year, Hamaguchi decided to enroll at the Berklee College of Music in a one-year jazz composition course to further his opportunities as an anime composer.