The purchase of the small but prestigious winery in the Santa Cruz mountains by Otsuka Pharmaceutical Co. was only the second by a Japanese concern. Sonoma Valley's Chateau St. Jean was bought for $40 million in 1984 by Suntory, Japan's largest wine maker and one of the world's largest beverage manufacturers. Ridge's four founders decided to sell the winery after concluding that none of their children was interested in entering the business. Terms of the sale were not disclosed. Current management and wine maker Paul Draper will continue under the new owners.