Approach on the Open Side/Exceptions

12th Honinbo match  

In game 6 of the 12th Honinbo match (Fujisawa Hosai, challenger vs. Takagawa Shukaku), Takagawa played .

In the commentary I (Bill) saw, there was no comment about this move. Factors behind Takagawa's move might be the White group on the right side, limiting Black's expansion there, the ability to play as an extension cum pincer from White's top left corner, and Black's moyo on the bottom. Allowing Black another moyo on top, albeit small, might have made for too easy a game for Black.

Exception 2

Absolutely necessary  

From Go Seigen's 21st Century Go, vol. 1, pp. 70-71.

This is not from a game, but a lesson. Go Seigen says that is an absolute necessity. If White gets to play instead, it will become difficult for Black to invade White's right side.