We start with the presentation of the later part of Our Solution (2015), which emerged after the kind advice of Prof. Jeong SooHyun 9p to start the endgame at the left side with the Tsuke of Yamada Shinji 6p "early", i.e. immediately after the creation of Black's nine-stone nakade at the left edge.

Even with the classical Nakade Sequence played before, KataGo's Immediate Crosscut will improve the result for White by three points.

However, wasting even a single move on occupying opponent's liberties in the Main Semeai before playing the in the Main Semeai before playing Yamada Shiji's Tsuke turns out to be a technical mistake:

One move too late - and previously uncritical subvariations develop an unexpected life of their own.

Two moves too late - and the chance is lost once and for all.

Several variations in which KataGo explore White spaces on the touristic map of Black's lower left corner should be particularly interesting.

Referenced by ( 2037), ( 2038), ( 2038)

Let's enter the world of professionals and look through the eyes of some help-seeking amateurs ...

( 2022MainLine)
This is the postion at the end of the Crosscut Sequence. The last move played was , which starts the Nakade Sequence.

Please note that at this time we had not played the "early" kikashi of , in the hanezeki.

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The game continues with the Nakade Sequence.

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White gives atari at Black's eight nakade stones.

KataGo's atari on the single Black stone below was still hidden in the mist of the future.

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During the friendly review of our results so far, Prof. Jeong SooHyun remarked that with the Main Semeai between White's group on the left and Black's group in the upper right already decided, right now would be the appropriate time to start the endgame on the left side of the board with Yamada Shinji's Tsuke.

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Immediately afterwards we added Black's kikashi in the hanezeki, assuming these would be absolute sente.

Later, some doubts arose about this, which is why we then brought this kikashi forward until just before the end of the Crosscut Sequence in the left centre.

However, according to KataGo's current assessment, our original timing would be quite possible. If one wanted to be on the sure side, one would let two more moves (, ) pass.

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Without giving much thought to the fundamentally different situation on the left edge (the two points are not yet occupied by Black stones), we simply adopted the original move sequence shown to us by Yamada Shinji.

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Only KataGo showed us that the immediate crosscut would have been better for White.

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Black ends in gote, when the sequence in the upper left corner comes to a temporary stop.

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We continued the endgame with Cheng's Bump in the left centre, not yet knowing KataGo's Wedge at .

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White's hasami-tsuke starts the reduction of Black's territory in the lower left corner.

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Again, Black ends in gote.

We continued with , capturing Black's nakade, not being aware of a hidden gem in the lower left corner, which will be unearthed by KataGo further below.

The capture of Black's nine-stone nakade.

We mistakenly assumed that the endgame on the left side of the board would be independent of the Main Semeai.

Only KataGo taught us better, as will be explained in detail below.

The mutual occupation of opponent's liberties in the Main Semeai.

The mutual occupation of opponent's liberties in the Main Semeai continued.

After Black's oki into White's four-point eye at the left, we have reached White's decision point.

White can choose between the Capture Variation (starting with ), and the Semeai Variation (starting with ), which will be better for her.

In Our Solution (2015) ...

The final scores of the game will become Black + 5 / Black + 3.

Let's find out what KataGo thinks about this matter ...

: (A 2043a)
White should play Yamada Shinji's Tsuke in the upper left immediately after Black completed his nine-stone nakade at the left edge with .

Continuing with the Main Semeai, e.g. wth in the right centre, can be considered a technical mistake.

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Black blocks.

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White plays KataGo's Immediate Crosscut.

Please note Black's two still missing moves in the lower border of his corner.

: (A 2043k)
Black must give atari at White's just played stone from the inside.

Trying to resist by giving atari from the outside is a grave mistake here, losing one point overall.

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White gives atari at the upper edge.

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White finishes the sequence in the upper left - for the time being.

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Black inserts his kikashi in the hanezeki now.

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Here, in this position without KataGo's Atari around the Nakade, it is better for Black to play the descent to the lower edge, stabilising his shape in the lower left, and also defending his territory in the lower left corner.

Playing the atari at at the upper edge would be one point worse, due to the remaining weaknesses of Black's large group at the left, which KataGo would be able to exploit.

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White pushes into Black's upper left corner.

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A Black kikashi.

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White continues in the upper left by giving atari at Black's two stones.

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Black captures White's cutting stone, of course.

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White connects her just played stone, also giving atari at Black's two stones.

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It is best for Black to connect.

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The Main Semeai continues.

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Black does not play any reduction.

Capture Variation:

Compared to Our Solution (2015), ...

• White's cumulated gain in the upper left corner is six points.
• White got an additional two points of territory at the top.
• Black's cumulated gain in the lower left corner is five points.

In total, White gained three points.

Black + 5 => Black + 2

Semeai Variation:

Compared to Our Solution (2015), ...

• White's cumulated gain in the upper left corner is six points.
• White got an additional two points of territory at the top.
  - Black's cumulated gain in the lower left corner is five points.

In total, White gained three points.

Black + 3 => Jigo

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