"Karate Bear Fighter" (1975) was based on the actual exploits of Sonny Chiba's teacher, Mas Oyama, a real life karate expert of Korean birth who was not only Chiba's teacher, but also the inspiration for Ryu from the Street Fighter games.
Ryu is a sanitized version of the very eccentric and insanely tough Mas Oyama's real personality. Oyama would not only fight bears and oxen publicly with his karate for attention, but would also go into the wilderness to train extensively as a hermit. He also lived, simultaneously, with his wife and girlfriend.