Yamazaki is a first champion of the All-Japan Full Contact Karate Open Championships in 1969, and has promoted Kyokushin famous through his accomplishments.

Because he fought and defeated Muay Thai boxers, he created a reputation for Kyokushin before the First All-Japan Open Full Contact Karate Championships was held.

For two and a half years Yamazaki commuted three hours from his house to the dojo, and reached the rank of shodan (1st degree black belt) on April 15, 1967.

[11] Yamazaki instructed pupils of novice, intermediate and advanced levels at the headquarters of Kyokushin and the U.S. Army Camp Zama besides his own practice.

He later said that it was good experience for him to instruct at Camp Zama as the pupils of the U.S. Army were larger than Japanese fighters.

Several pupils measured over 200 centimeters in height and weighed over 90 kilograms, and practicing with these students led him to develop new ways to fight and knock out larger opponents.

TV Asahi requested a player from Kyokushin in February, 1969, and Masutatsu Ōyama elected Yamazaki and Yoshiji Soeno to enter the competitions.

At the first competition, Soeno fought Kannanpai who was one of the strongest boxers of Muay Thai and had won over Tadashi Sawamura a half a year before their match.

[13][14] After these fights, Yamazaki wanted to learn Muay Thai because it is a strong and technical martial art.

[1] He fought ten kickboxing matches with a record of eight knock out wins and two losses (two lost on a decision).

[2][3] Kyokushin was planning to hold the First All-Japan Full Contact Karate Open Championships at the Tokyo Metropolitan Gymnasium in September 1969.

The rules were simple: It was a foul to use a hand or elbow to the face and to attack a man's vital point.

[14] His karate training had decreased because he graduated university and began to work as a television producer after the Second All-Japan Open Championships.

[7] All concerned in Kyokushin and the mass media were surprised at Yamazaki's performance at the Fifth All-Japan Full Contact Karate Open Championships in 1973 because he didn't have a chance to train sufficiently before the competition.

Yamazaki left a steady record of wins in all of the All-Japan Open Championships in which he participated.

For this reason, the dojo was not called Kyokushin but instead Fuurinkazan (風林火山) from his hometown hero Shingen Takeda.

All-Japan Full Contact Karate Open Championships and World Full Contact Karate Open Championships included a breaking competition as well as kumite, with players required to demonstrate breaking of cryptomeria boards.

Competitors could use four types of technique: punching (“tsuki"), kicking (“keri"),　knifehand strike, and elbow.

This record was not broken for a while, but it was exceeded in total breaking and reached a new height with Willie Williams, a karateka from the United States, at the Second World Full Contact Karate Open Championships in 1979.

Some fighters who have benefited by studying under Yamazaki are Katsuaki Satō,[6] Miyuki Miura,[22] Seiji Isobe (teacher of Glaube Feitosa, Francisco Filho and Andrews Nakahara),[23] Howard Collins,[9] Toshikazu Satō (champion of the Eighth All-Japan Full Contact Karate Open Championships),[19] Takashi Azuma (champion of the Ninth All-Japan Open Championships),[20] Makoto Nakamura (Two times champions of the Second and Third World Full Contact Karate Open Championships)[24] and Shokei Matsui.

[21] After the First World Full Contact Karate Open Championships in 1975, Yamazaki visited Shigeru Ōyama's dojo at White Plains, New York.