For Kazuo KOIKE set up a role of villain named 'Retsudo YAGYU' in his work of period drama, "Kozure Okami" (Lone Wolf and Cub), this image has become predominant and it seems that his real person and fictitious images have been mixed up.
小池一夫が時代劇作品の『子連れ狼』で「柳生烈堂」という名で悪役に設定したため、現在ではそのイメージが強くなり、実像が虚像と入り混じってしまっている感もある。