BQM 561

Corner sequence  

is a surprising move. It was played as soon as move in the Honinbo finals of 2014 between Ida (include link) and Iyama Yuta.

Reversal  

- reverts to a known joseki: 4-4 point low approach low extension, contact

Reversal 2  

This is the refutation given in Lee Chang Ho's Hamete book. He has the one space jump at a instead of knight's move for black, but the idea is the same: revert to joseki but with white pushing in the corner instead of extending down the side, which is usually a bad choice for white.

The same answer appears in Graded go problems for dan players volume 2. Again with the one point jump instead of the keima

Tenuki  

Tenuki is a sort of standard idea to punish this. Where can white invest a followup move that doesn't leave the large knight's move cut? Attacking at a or thereabouts is similar.

Ladder  

If the ladder works for Black, he can play like this. This is also mentioned in Graded go problems for dan players volume 2 (with the one space jump instead of the keima). It is good for black as the white corner is small and Black is thick. Instead ...

White leaves a weakness behind  

... here White takes the corner again but leaves Black with a possible weak point around a. But this doesn't look like it's a good idea with a Black keima instead. However White has yet another move:

Ladder  

The clamp of is suggested as a peaceful answer. The sequence up to is called even (in aforementioned book). This way of playing seems practicable with the keima too. These two sequences are the reason why the book suggests the diagonal at a rather than as an answer to the white ogeima.

Corner sequence  

in this sequence is not joseki and this BQM is about answering this the best way possible for black.

Continuation from the game  

at

In the game, it played out this way. Black had no suitable ko threat and got a very bad result when connected at

Even if black had connected, it seems to me like white would be satisfied has black has a small corner when white has a large influence from his ponnuki.

Too mild for black: white returns to joseki  

The original thread on reddit proposed the san-san ( in the next diagram) as a good answer to the surprising white move, but then white can return to a joseki position with

Atulab's sequence  

Next moves at a, b and c

One possible way I thought about ressembles another 4-4 joseki:

at would be impossible in the game: the ladder is good for white. This seems to me like gets developpment on both sides when white has a small corner, but maybe I'm not assessing the position correctly

What do the senseis think ?

Corner sequence  

HermanHiddema: is an idea.

Corner sequence  

If white pulls back with , this is disastrous.

Corner sequence  

This looks more reasonable for white, but he is still low, and his position is not without aji.

Another possible sequence  

MrTenuki: What about this ( at a if the ladder is unfavorable)?

Corner sequence  

Andy: How about simply proceeding according to the usual joseki followed by a tenuki from black where now looks slow?

Uberdude: This is the refutation given in Lee Chang Ho's Hamete book. He has the one space jump instead of knight's move for black, but the idea is the same: revert to joseki but with white pushing in the corner instead of extending down the side, which is usually a bad choice for white.

fractic: The same answer appears in Graded go problems for dan players volume 2. Again with the one point jump instead of the keima.

White's development?  

Slarty: Tenuki is a sort of standard idea to punish this. Where can white invest a followup move that doesn't leave the large knight's move cut? Attacking at a or thereabouts is similar.

Ladder  

Dieter: If the ladder works, I'd play like this.

fractic: The book I mentioned above has this sequence too (with the one space jump instead of the keima). It calls it good for black as the white corner is small and Black is thick. They suggest the sequence below for White instead.

White leaves a weakness behind  

fractic: Here White takes the corner again but leaves Black with a possible weak point around a. But this doesn't look like it's a good idea with a Black keima instead. However White has yet another move

Ladder  

fractic: The clamp of is suggested as a peaceful answer. The sequence up to is called even. This way of playing seems practicable with the keima too. These two sequences are the reason why the book suggests the diagonal at a rather than as an answer to the white ogeima.

Dieter: Really? That looks awful for White.

fractic: I disagree. I don't think it differs that much from the usual keima slide joseki. White has a bit poorer eyespace but on the other hand Black's corner is a bit smaller.

Dieter: This shape is not found in any pro game on gobase. There must be something wrong with it and the premature first line connection of is a likely candidate. In the beginning of a game stones are looking for eyespace, not for territory reduction.

No eyes  

There is no eye for White in the corner, since Black can play . So these stones are dead weight for White, in the opening and middle game. In the endgame, territory reduction is worthwhile. Also, the marked white stones form a weak diagonal, that can be compromised at a, so that any support from the top right can become dangerous.

I would not call it desastrous for White, but I cannot see the point of playing this way. I'm curious about what the book exactly says.

fractic: The book shows the position after the white ogeima and then shows the diagonal attachment as correct. But does not mention the jump-attachment in the solution diagrams. However the next problem is White to play from that position. The two diagrams I gave above are both marked correct. While the wedge is labeled a rash move. Which is then analysed in the next problem. showing some of the diagrams that appear on this page.

When I said "This was the reason why..." I was referring to both diagrams not just the second sequence. But I have to admit it looks like I'm only pointing to the second diagram. I'll modify my original text.

Not as mild for black, with B  

Slarty: One difference between the one space jump and the keima is that (mentioned above) is worse. White's breaking through tactic at and is quite successful against the keima, but not so with and . (4 is more commonly a double hane at 6 - this has the same issue with 7 and 9.)

Another difference from the original is that if black ignores , white has a good followup move at a.

I still feel strongly that in the original position, lowers the temperature substantially. Immediately choosing a local reply has a danger of giving white one or more options that make her stones work.