Ryuji Aigase is a Japanese actor and voice actor born on July 2, 1987, in Hirakata, Osaka Prefecture. His blood type is O. He began his career in entertainment as a child actor, having been a member of the Tokyo Children's Theatre. From 1995, he appeared on the NHK educational program "Tensai Terebi-kun" as a "Terebi Senshi" (Television Warrior) for a period of three years.

Aigase is primarily known for his voice work in anime and animated projects. One of his most significant and defining roles is that of Hermes, the talking motorcycle, in the "Kino's Journey" franchise. He first voiced the character in the 2003 anime television series "Kino no Tabi: The Beautiful World". He reprised this role in subsequent installments, including the 2005 original video animation "Kino's Journey: Life Goes On" and the 2007 film "Kino's Journey: The Country of Illness -For You-". His portrayal of Hermes also extended to the 2009 video game "Dengeki Bunko RPG: Cross of Venus".

Beyond his iconic role in "Kino's Journey," Aigase's other voice acting credits include the character Colonel MacDougal in the 1998 animated film "Spriggan". He also had a role in the 1998 television series "Ultraman Dyna". His filmography includes a part in the 2011 animated film "Legend of the Millennium Dragon" (also known as "Onigamiden") and a role in the "Short Peace" anthology film from 2013. He was approximately sixteen or seventeen years old when he first took on the role of Hermes in the 2003 anime series.