, was the strongest and most famous amateur Go

Go (board game)

Go , is an ancient board game for two players that originated in China more than 2,000 years ago...

 player of the 20th century in Japan. As a professional Go journalist, author and editor, and long-time undisputed strongest amateur player in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, Yasunaga was personally acquainted with most of the strong Japanese professional

Go professional

A Go professional is a professional player of the game of Go. The minimum standard to acquire a professional diploma through one of the major go organisations is very high. The competition is tremendous, and prize incentives for champion players are very large...

 players from the 1920s to the 1980s.

Shin Fuseki Ho

In the early 1930s he co-wrote Shin Fuseki Ho, a seminal work on go opening theory, in cooperation with the young professionals Kitani Minoru and Go Seigen. The book created a sensation, and helped win amateur players over to the revolutionary ideas of shin fuseki

Fuseki

Fuseki is the whole board opening in the game of Go.-Less systematic:Since each move is typically isolated and unforced , patterns for play on the whole board have seen much less systematic study than for Joseki, which are often contact moves which require specific and immediate responses...

 ("new opening") theory.

Representing Japan

Yasunaga twice represented Japan in the World Amateur Go Championship

World Amateur Go Championship

The World Amateur Go Championship is an international tournament for amateur Go players, held once a year since 1979. The organising body is the International Go Federation . Each participating country sends one player, although in the beginning of the contest there were multiple players from the...

, first in the inaugural tournament (when he was 77), and then again three years later when he was 80. He acquitted himself well in both tournaments, but was not able to prevail against the strong fields of younger players. He also taught a number of professionals, including Komatsu Hideki and Kageyama Toshiro and Yokoyama Koichi. It has been said that at his peak, Yasunaga was sometimes able to defeat inexperienced young professional players while giving them two-stone handicaps.

Yasunaga played against Chen Zude

Chen Zude

Chen Zude is a Chinese professional Go player. He was also the President of the Chinese Chess Association.-Go career:...

in the 1963 China-Japan Supergo event.