Gokyo Shumyo, Section 1, Problem 26 / Solution

Main line  

The tesuji here is . After , Black can't create a dead shape with a, because he is in shortage of liberties (this is oshitsubushi). Note what a difference a black stone on the marked point would make.

Variation 1  

White has to be careful to answer at and not at . The strength of is precisely that it already prevents the connection underneath.

Variation 2  

Answering at is the only move. It appears as if White can destroy the eye after this sequence by throwing in again at , but White will simply connect at a.

Variation 3  

Just to clarify: If Black tries to leave White with a big eye by connecting at a (almost filling the enclosed space with the dead shape of three in a line), White runs to b and claims a second eye at c.

How should White then respond if Black tries playing at d? That won't work for Black; White runs along the second line and if Black follows, eventually White can block on the first line and the resulting capture will give the second eye (at least). I don't think playing at e directly will work; seems like Black sets up a ko that way. White could probably also escape in this sort of situation. -- KarlKnechtel

Wrong 1  

Black's hane produces a ko

Wrong 2  

Black kills with the same hane.

White lives?  

After , can white live?

White lives  

Why not the simple descent of ? This makes miai of a and b, no?