Among the designers with whom he apprenticed are Junko Koshino and Hisashi Hosono; in 1971, he opened his own company, Yamamoto Kansai Company, Ltd., Tokyo. His first collection debuted in London in 1971 and in the USA at Hess's Department Store in Allentown, Pennsylvania, which was renowned for many avant-garde colletions. His 1975 debut in Paris was followed by the opening of his Kansai Boutique in 1977.
In 1999 he organized a fashion program under the aegis of the India-Japan Mixed Cultural Cooperation Committee.
Since 2001, he has been known for his fashion eyewear, sold by Aoyama USA.
Yamamoto is Kabuki in his overt theatricality, flamboyant sense of gesture and design, and brilliant colorful design as much to be read from afar as admired at close range. Gaudy by desire, larger-than-life by theater's intensity, and virtually to Japanese culture what Pop style was to Anglo-American culture, Yamamoto has consistently cultivated a fashion of fantastic images, extravagant imagination, and sensuous approach to both tradition and a view of the future.
Central to Yamamoto's work is his delight in mass entertainment and popular culture, a sense of both following and leading the ordinary population whether in graphic t-shirts or the convenience of knitwear. His silhouettes for both menswear and womenswear are extreme, suggesting either the most wondrous last samurai or the most magnificent first warriors for intergalactic futures; his appliqués have been in the ambiguous realm between primitive art and 20th-century abstraction.