Koyama is reputated as an experienced rescuer who can react quickly to hazardous situations. Contrary to his gentle appearance shown during the most of time, he demonstrates a strong mentality whenever he is on duty.
Koyama joined a NGO based in the war-torn Bosnia and Herzegovina and became a voluntary rescuer there at the age of 18. During an unspecific period prior to his career at XIG, Koyama also worked as a rescuer in Cambodia.
- According to the "Early Character Plan" edited by Chiaki J. Konaka, Koyama is born in Samani, Hokkaido.
- His actor Shunsuke Gondo is famously known for his role as the suit actor (slimmer form) for Ultraman Tiga, Ultraman Dyna and Ultraman Gaia.
- Since Gondo has the prominent roles in Gaia Again OVA , Koji Nakamura played in a suit for both V2 and Supreme Version for Ultraman Gaia.