As Wikipedia states:
In 1933, along with his great friend Kitani Minoru, Go Seigen developed and popularized the shin fuseki ["new opening" theory] that broke away from the traditional opening patterns. It is for this very important contribution that Go Seigen and Kitani Minoru are recognized as the fathers of modern Go.This happened during a series of matches between the two great players. The games of the match are described in detail in a very good book by John Fairbarn, Kamakura (named after the temple in which the match series happened). The author describes both the games themselves, with deep but accessible analysis, and the historical background surrounding each game. You can read the few excerpts from the book here.
An episode from the movie about Go Seigen, The Master of Go, that shows the first of the matches: