According to the Anime News Network, as of December 2008, Koyasu is the most prolific seiyū in Japan with voice acting roles in 365 anime series. He is also the creator of Weiss Kreuz and part of the seiyū quartet Weiss consisting of Weiss Kreuz voice castmates Shinichiro Miki, Tomokazu Seki, and Hiro Yūki. He used to work for Production Baobab but is now the head of T's Factory, a seiyū company he founded in 1998.
Roles in Hokuto no Ken mediaEdit
Shin Hokuto no Ken (2003-2004 OVA series) - Kenshiro Edit
- Hokuto Musou (2010 video game) - Rei
- Shin Hokuto Musou (2012 video game) - Rei
- Souten no Ken Regenesis - Liu Feiyan