Koyama Dojo HDRJJ is a martial arts school in Livonia, Michigan offering adult self-defense and traditional Japanese JuJutsu classes. The dojo serves as the Honbu Dojo for Hakko Denshin Ryu JuJutsu in North America and is part of the global Hakko Denshin Ryu Federation. Instruction emphasizes practical self-defense through leverage, body mechanics, and structure rather than size or strength, with one-on-one Shihan/Deshi style teaching from instructors with over 25 years of experience. Classes are held for adults on Monday and Friday evenings and Saturday mornings.