Last week, we talked about how to set up the sanrensei position with 1, 3, and 5, and about the various responses to White 6. This week, we will look at Black 7 and subsequent follow-ups. In response to 6, locally Black can play at A, a common move if Black 5 is absent. Even if Black 5 is already in place, playing at A is possible. However, I feel this is inconsistent with the philosophy behind the sanrensei of building a huge moyo. In general, moves on the third line (like A) are territory oriented, while the fourth line is for building influence.
White will now usually play at 8 or B to back up his stone at 6. Black has the choice between playing at 9, at C, or around D. There is actually a subtle difference between a White stone at 8 or at B and this has an impact on our choices here. However, this goes beyond the scope of this week’s discussion. We will return to it at a later stage, during the Kobayashi fuseki in this series on openings. Before continuing from move 9, let’s first explore Black C and D.

After White 8, if Black decides to play in the top left, he can choose between 9 and 17. Black 17 is a high-level move which we will discuss as part of the Kobayashi fuseki. For now, we will restrict ourselves to 9. White will usually pincer at or near B, or else play at 10. If White had played 8 at A, then white 10 would create an overconcentrated position. However, with 8 in place, White builds up a thick position in the top left, with a strong claim to the territory at the top. After 18, Black can defend his stones in the top left, or he can leave them as they are and switch to 19 or thereabouts. The only issue Black really has to keep in mind is that any stones in the top left should not become a weak group. In this position a weak black group anywhere on the left side, at the top, or at the bottom means the moyo on the right will suffer.

 

With the marked White stones in place, Black will usually not make a kakari on the third line with 1. There are several reasons for this, both philosophical ones and practical ones. Conceptually, the third line is the line for making territory, but also the line for making life. In contrast, the fourth line is the line of influence as well as making sabaki. That is a technical word denoting light shape, i.e. a shape that is flexible and can easily run away. In practical terms that means Black 1 is slow and doesn’t have a lot of flexibility towards the center. One joseki is the sequence shown. Arguably, the choice here is self-serving, but you can see that the marked White stones are in just the right place.

 

Black can play a keima kakari at 9, and if White tamely answers at 10 then Black obtains an ideal position with 11. It is far more likely that White will resist and pincer at A or B. This will result in a fight that is not necessarily bad for Black. If you like fighting, give it a try sometime. But if you like to keep it simple, it is better to play as in Diagram 5.

 

As explained, Black 9 is the easy move. In order not to suffer the same result as in the previous diagram, White could extend to 10. Black could view this exchange as a kikashi and switch to the top left. After the moves through 20, Black 21 offers some protection for this group, but now White will invade. In this shape, 22 is the right point for invading. Black 23 prevents White from connecting underneath, so White moves out into the open with 24. Since White has jumped out to the center farther than Black, technically he has the initiative. This is true all the more because Black needs to defend around A, allowing White to cap in the center around B.

 

The way to defend is very interesting. Black 13 defends the corner and the right side while defending indirectly against the invasion. However, this requires a bit of preparation: Black should first exchange 11 for 12. When White does invade at 14, as you can see, Black seizes the initiative with 15 and 17. Now compare this result to the one in Diagram 4: even if White moves out into the center, Black has already defended at 13, so he can attack strongly in the center.

 

You could argue that Black 13 gives even more protection against the invasion. However, now White will invade on the right. Common invasion points to do so are A, B, and C. Although this is not an immediate threat, White is also aiming at cutting at D. In the end, Black 13 is too direct as a defense and in that sense is lopsided.
Pros try to avoid such one-dimensional moves, but I think you should experiment with both moves until you can muster the confidence to play moves that defend indirectly.