When Yuzan grew up, he went to Edo and learned military science of Koshu school from Kagenori OBATA, Ujinaga HOJO, Soko YAMAGA and others, and established himself as a scholar of military science.
友山は長ずるに及んで江戸に出て、小幡景憲、北条氏長、山鹿素行らに師事して甲州流軍学を学び、軍学者として身を立てる。