4-5 point 4-3 approach ogeima

The ogeima at is rare, because it lacks a strong follow-up move: it's easy for white to tenuki. See 4-5 point Josekis for the more popular options.

After the ogeima, white may:

• jump to a, which is treated here;
• choose the contact play b ("risky" according to Ishida, "not joseki" according to modern Chinese joseki books, but only a fraction of a point worse than other options according to KataGo): see 4-5 point 4-3 approach ogeima, contact;
• tenuki: see 4-5 point 4-3 approach ogeima, tenuki.

Hanmanchu: Even c, d and e are possible in this position.

Variations for the jump

After the jump, black has two options: a and b.

Black a transposes to the following joseki: 4-5 point 4-3 approach keima, contact at 6-3, which will end in sente for White.

If b, White ends in gote this way, but gets ahead on the left side.

Hanmanchu: In Lexikon der Joseki II it says equal / "ausgeglichen", BUT in general this variation is not too good for White, because the ponnuki gives too much thickness to Black. Instead of letting be captured, better stretch once with at .

Playing at or at a in this diagram might be better options.

White can now cut at a.

Now Black may cut at a.

Variations for the kosumi

It's very logical. If next Black a, White can cut at b.

Mistakes

If hane on the outside, then will cut Black at the elephant's eye. White's table shape is good while Black's shape is broken. Compare the variations at 3-4 point high approach, two-space high pincer, ogeima; the difference here is the exchange of the circled stones, which is bad for black in this position.

Increasing the sacrifice for tempo gain, as with here, is not good in this case. does not get ahead as in the joseki variation, while is hurt. Black indeed still needs to capture the cutting stones (a?) but his shapes are strong so he might jump ahead to c. (Dieter: this diagram needs confirmation. xela: Actually, KataGo likes this variation. It's the position described by Hanmanchu's comment above, "instead of letting be captured, better stretch once with at ", yes? Hanmanchu: yes :) )

Hanmanchu: Yes, c seems to be the correct local continuation. See for example Lexikon der Joseki II, page 308.

xela: KataGo suggests that d might be even better than c, depending on the full board context. Remember that Lexikon der Joseki predates the AI revolution.

Hanmanchu: Of course you are right with your comment regarding AI joseki and I am aware of the many developments happening. I wanted to try to answer Dieter's question above.

The ogeima in pro games

(Note that the Shusaku game move is handled at 4-5 point 4-3 approach ogeima, contact)

Here the ogeima also serves as an extension from the marked stones, which should be easy to understand.

and are best. was a mistake (attaching at was better according to KataGo). was also a mistake: instead simply pushing to was better. , giving Black the ponnuki, is bad. finishes the situation locally, but b is a very good move for Black now. Black played ata, also a good point.

Instead of , KataGo thinks any of c, d or e are about equally good.