4-5 point 4-3 approach inside contact, follow-ups

Black has some aggressive plays  

Assuming White took sente at the end of this joseki, Black gets a chance to attack White.

According to the position as a whole, Black may wish to attack directly at the circle-marked point (a vital point of the diagonal of the stones); or to build influence with the cover at the square-marked point (discussed at order of play - temptation).

Direct attack  

Suppose Black applies the direct approach . Then the pros usually come out at a. The play at b is a tesuji to help White gain immediate life.

Standard fight  

After here, the inducing move at is taught as tesuji. It is possible for White simply to play at c'.

Continuation  

This is a normal result: at will lead to nothing good for Black.

A low position  

If instead , Black usually plays this way, treating White's play as submissive.

A possible ko  

This is from a game Hashimoto Utaro-Suzuki Kensho (B), 1950-01-12. If here, it makes no sense to go back later to the circled point to play hane, after Black has filled in a liberty. So we get . Now it can become ko.

Game continuation  

There was no actual ko: White sacrificed the stones and in return weakened , as a big exchange happened.

White is thick  

Simply playing here gives White a high position, that is quite thick from fighting perspective. Later White can hope for White a, Black b as forcing.

One line more  

If instead here, White's shape is more efficient. But in this case Black can hope for a forcing exchange Black a-White b. That has an effect on any later white invasion at the circled point.

The tighter choice of is therefore generally seen, in pro games.

Charles Matthews