He is notable for being the first Japanese player to play for a Major League Baseball team. Sent over to the United States by the Nankai Hawks, Murakami saw success as a reliever for the San Francisco Giants, debuting at the age of 20 in 1964. In 1965, he struck out over one batter per inning pitched, posted an ERA under 4 and earned eight saves. Following this season, however, Murakami headed back to his original Japanese club due to contractual obligations, where his success continued for another 17 years.
Murakami entered the Japanese Pacific League professional team, the Nankai Hawks, in September 1962, while still attending high school. In 1964, his team sent him, along with two other young players, to the San Francisco Giants single-A team Fresno as a baseball "exchange student". He was originally only scheduled to stay in the United States until June, but the Hawks neglected to call him back to Japan, and he stayed with the Giants for the rest of the season. In August of the same year, he was promoted to the majors, and on September 1, 1964, he became the first Japanese player to play in the major leagues and the first Asian-born player since Chinese-born Harry Kingman's cup of coffee 50 years earlier. Murakami pitched extremely well as a reliever, and because of it, the Giants refused the Hawks' order to return him to Japan. The argument escalated during the 1964 off-season, and Japanese baseball commissioner Yushi Uchimura was called in to make the final decision on which team Murakami would play with. The commissioner made a compromise; Murakami would return to the Hawks after he had played for another full season with the Giants. He wore number 10 with the San Francisco Giants.
Murakami returned to the Hawks in 1966, but failed to live up to the team's high expectations. He proved himself by winning 18 games in 1968, and contributed to the team's league championship in 1973, but was traded to the Hanshin Tigers in the 1974 off-season. He did not pitch well, and the Tigers released him after one year, but the Nippon Ham Fighters picked him up. He made a comeback in 1978, winning 12 games, and contributing to the team's league championship in 1981. Murakami retired in 1982, but returned to the San Francisco Giants spring camp in 1983. He was not signed as a player, but became a batting practice pitcher for Giants' home games.
He worked as a commentator from 1984 to 1986, and became a minor league pitching coach for the Nippon Ham Fighters from 1987 to 1988. He also served as a pitching coach for the Fukuoka Daiei Hawks and Seibu Lions. He also briefly worked as a scout for the San Francisco Giants, and is now a commentator for NHK major league baseball games, and writes for the Daily Sports newspaper.
In 2004, Murakami was presented with the Foreign Minister's Certificate of Commendation in commemoration of the 150th anniversary of the Japan-US relationship by the Ministry of Foreign Affairs of Japan.
Murakami was honored by the San Francisco Giants at AT&T Park on Friday, May 16, 2008, when a limited edition Murakami bobblehead was given away at the evening game against the Chicago White Sox as part of the team's "Japanese Heritage Night" promotion. He was again honored on the 50th anniversary of his debut on Friday, May 15, 2014 during the team's "Japanese Heritage Night" promotion and game attendees were given a figuring-style bust of Murakami, and threw out the first pitch of the game.
Murakami was not an overpowering pitcher. His fastball was only in the low to mid 80 mph range, even during his prime. His best pitch was a sharp screwball, which he learned in the majors, and he also threw a good changeup and curve. He was a valuable reliever, being a left-hander throwing from the sidearm. His total record in two years in the majors was 5–1, 9 saves, with a 3.43 ERA in 54 games.
He could barely speak or understand English when he first came to the United States, and always had a dictionary on hand to communicate with teammates. When promoted to the majors, he was told to go to New York City (where the San Francisco Giants were playing), and was given his plane ticket on the spot. In New York, he signed a major league contract even though he could not read a single word written on the contract.
The authors of 1973's semi-satirical reference, The Great American Baseball Card Flipping, Trading and Bubble Gum Book, stated that Murakami was "with the possible exception of Yogi Berra, the only major league ballplayer who did not speak English."