Opposing 3-4 Points

Symmetry creates tension  

This formation has been studied over centuries, because first-player advantage is large. (In Japanese these opposing 3-4 points are called kenka komoku (fighting komoku).)

Approach plays  

This is a normal development. White breaks the symmetry in order not to play into White a, Black b which is an ideal double-purpose play of pincer combined with extension. Now we expect a pincer to be played by Black in the right-hand corner. At c has been well explored, but d and e are played now. Yang Yilun recommends f (in How to Destroy and Preserve)...f is a dual purpose move serving as both a five space extension from and a pincer of . Thus f is urgent.

In the background is the press at g for Black.

In Edo period theory the high approach at wasn't yet widely played, so that the initial formation was generally avoided. Of course White could play out the left-hand corner instead, but the feeling is that an approach is a little more urgent.

A modern pattern  

This is quite a popular diagonal fuseki in professional Go. Black plays into mukai komoku on the theory that White will take the fourth corner, leaving Black with sente on the left side.

Charles Matthews