I started to think about this after Yoshida was signed by the Red Sox. The Dodgers were one of the first teams to dive into the Asian market. The Giants were the first team to ever have an Asian player when they signed Masanori Murakami back in 1964. He saw some success as a reliever. His last season with SF was 1965, It would be 30 years before another would come to the US.
The first Japanese player to play in the Major leagues since Murakami, signed with the Dodgers in 1995.