ThorAvaTahr: The diagrams shows a very popular, modern fuseki. The idea about the tsuke underneath the shimari is to prevent white from being closed in. Although black's shimari becomes solid territory, white's group is more secure.
Andy: Can someone please supply winning percentages with this fuseki when played by the pros? I see this quite frequently on KGS but offhand it doesn't seem that great for white. Black has two unassailable good-size corners and white's thickness is encroached on both sides by black and it is black's turn. In a related question, where does black usually play next after this formation is completed?
ThorAvaTahr: Interestingly many amateurs share your feeling. However, remember that white has komi. It is relevant, because typically black's plan is to use his starting advantage to make a large framework, in which he generates synergy from his starting stone. That plan is counteracted by white after this fuseki. Also note that black pushes from behind on the second line three times!!!
To answer your question, in a quick database search I found 56 games where the pattern at the left side was played 32 of these where won by white. The games inluded a wide variety of players, no player showed up more than two times in the list.
In this particular fuseki (with the white stones on the right placed as they show in the diagram) black usually plays 'a'. In the database search in 10 out of 13 games black played 'a', resulting in 5 wins. 'b' (2 games) and 'c' (1 game) show up as well but black lost all of these games.
Andy: If Black pushes from behind three times, does that mean Black is unimpressed with White's thickness?
ThorAvaTahr: Instead of diagram 2 my opponent played as in this diagram. In my limited professional database (only 45k out of 60k games) I found 90 hits on the fuseki, but noone played as in this diagram. Therefore, I expect that this line is inferior. My question is, how can white profit from ? Any ideas or comments?
ThorAvaTahr: One idea is to play as in this diagram.
Tapir: Isn't white overconcentrated with b-e sequence later?
kb: See the analysis below why White at a before is better. However, this is still playable, but with one line lower (good shape both directions).
kb: The reason why Black makes the - exchange is to make a White block on the right gote; otherwise would be bad because it is pushing from behind and on the second line. (Normally, a second push on the second line is to avoid the block becoming sente, but because there is already a cutting stone a third push is needed).
Directly playing at is not good.
kb: is normally a probe in this position (with the / exchange); Black responds with a-c or tenuki (which is probably not good in the opening).
- Ba is most frequent; White gains a little more security with the aji of the cutting stone.
- Bb takes more influence at the cost of Wc becoming sente, since now Black must answer Wd with Be.
- Bc has been played once but White gains a lot of influence in the center and a rock-solid group.
kb: However, in this case, must be answered locally by a; otherwise White can capture the stones. Therefore you could play - here; Black has been pushed around. (If you play first, Black replies with ; then can be answered at b.)
ThorAvaTahr: Thank you for your excellent description of the theory behind the fuseki. I agree completely. And as I mentioned earlier, I would like to exchange for before blocking. After that I have a satisfactory result. However, my fear is that black will answer with . After which it becomes difficult to get a good result. Therefore I am afraid I am forced to block immediately and give up the / exchange.
kb: First of all, I wouldn't call it a bad result. Actually, it is good for White!
kb: This looks like a little better for White. White got in sente, has a more secure group than the joseki and has good follow-up moves, e.g. a and b. Remember, Black got three moves on the right first!
ThorAvaTahr: Hmm, looks interesting indeed. I'll have to think about it. Perhaps 'c' would be more appropriate than here?
kb: Nevertheless, if you don't like it, you can just respond like this, which transposes back to joseki:
ThorAvaTahr: No, I do not want to revert, I think black made a mistake and I am greedy ;)
kb: By the way, I have had one opponent ignore the probe and cut at the lower right. My teacher advised me to ignore him too ;)
Dieter: And I guess that answering on the outside with , allowing White to return to the classical joseki, leaving a behind, is too passive for Black?
kb: Absolutely. Black trading b for c isn't good, because White still has a, therefore later White can play one point above b and Black is stuck.
In another light, tewari tells us that if - is played first, then Black will never answer with because the outside is no longer important.