We will shed light on the mistery of Fujisawa Hideyuki 9p rejecting a second throw-in in the hanezeki, but not be able to really penetrate to the core of his reflections.

We will follow the chronological sequence of findings on this move and deduct that my Second Throw-in would not affect the relationship of liberties in the hanezeki, but benefit Black territorially in both Main Variations.

Choosing Harry's Hasami-Tsuke Sequence for the reduction of White's upper left corner in due time would not only increase Black's flexibility in the game, but also affect the overall result, as KataGo discovered. Black would be able to benefit by another point overall.

Referenced by ( 2022MainLine)

Let's go back to the dawn of time ...

: ( 2022MainLine)
This is the position in the classical sequence by Fujisawa Hideyuki 9p, when Black solidly connects his stones in the upper right in order to form one large group.

Black can do so in sente, as Black threatens to exploit White's shortage of liberties with , , , aiming at a snap-back.

Black's connection defends against the forcing sequence (threatens to create an eye), , , , which White would otherwise play at the earliest possible moment, and which would take Black's large group a decisive Main Semeai Liberty.

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White fills one of her false eyes.

This move stops Black from playing my Second Throw-in , which will be explained in detail below, later in the game.

In principle, White might alternatively fill the other false eye at , as Fujisawa Hideyuki rejected my Second Throw-in anyway.

Decades later, in the world of amateurs ...

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Black throws-in for the second time, which is the correct continuation here.

In his commentary, Fujisawa Hideyuki unfortunately did not elaborate in detail on what was the actual reason for his rejection of this move.
He only mentioned that his line of play avoids filling a liberty of Black's large group, which would not be good.

However, even after a very long search I could not find any semeai for which my Second Throw-in would result in a disadvantage for Black.

Please note that my Second Throw-in must be played just now, as Black's group at the right edge lost a decisive liberty at as a result of the first throw-in at .

If Black continued with , White would connect at in sente, threatening to capture Black's hanezeki group below. Black would have to take White's group a liberty with , reverting to Fujisawa Hideyuki's original line of play.

Before this exchange in the right centre, however, the upper kikashi in the hanezeki , would have to be inserted, as found by Cheng in his 1988 book (see below).

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White has to capture Black's just played stone.

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As in the classical line of play, Black's connection at is mandatory now.

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White fills her upper false eye, in order to erase her damezumari.

It threatened Black's atari at , which White would be unable to connect with successfully, due to .

Alternatively, White could also fill her lower false eye with .

Years later in China ...

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Cheng also used my Second Throw-in in his 2010 book on Igo Hatsuyōron (but not in his original 1988 one).

This was not particularly surprising, because our collected findings as of June 2008, which we had handed over to the head of the Chinese Professional Go Organisation with a polite - but unanswered - request for qualitative feedback, had quite obviously been passed on to him.

Let's return to the amateur era, enter the amateur analysis room, and stay there for a while ...

In essence, Fujisawa Hideyuki's reasoning means that Black would have to swear off the loss of a shared liberty with White's group in the (temporary) seki below.

The loss of one liberty is relevant only in the Capture Variation, as Black's large group will be taken off the board in the Semeai Variation anyway.
This means that we have to determine the effects of the different scenarios primarily for the Capture Variation.

In the course of the resolution of the hanezeki in the Capture Variation, White's group will be taken off the board.

Only afterwards can Black deal with eliminating the next group.

The all-deciding question is:

Can Black succeed with the Punishment Semeai and prevent his group from being taken off the board??

In order to compare the various scenarios, we will determine how many moves Black needs for occupying the "outside" liberties of White's upper group in the hanezeki until it is in atari.

We will see below that the shared liberties above White's group do not really matter in this context.

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For some other reason, Black will play these kikashi in the hanezeki, which are Black's priviledge, "early" (as KataGo also does).

The need to play the upper kikashi at "early" was discovered by Cheng in 1988, but exists in the classical solution only.
With my Second Throw-in played, it is not necessary to play these kikashi in the hanezeki so early in the game.

For further details, please refer to section "Kikashi in the Hanezeki" ( 2027)

In contrast, the lower kikashi with the atari at is not mandatory even in the classical line of play and could be waived until the end.

Capture Variation:

Black needs one move to give atari at White's group.

Let's go back in time again and look over Fujisawa Hideyuki's shoulder ...

This is the comparable position in the Fujisawa Hideyuki's line of play, after Black's forcing exchange , .

Capture Variation:

Black needs two moves to give atari at White's group.

Half a decade later in China ...

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The kikashi of is White's priviledge, explained by Cheng in his 1988 book.

Black is forced to occupy a shared liberty with , in order to prevent his group below from becoming captured.

Please note that White will not play the second forcing exchange , before her decision point, as it would lose points in the Capture Variation unnecessarily.

Black's stones and will provide White with an additional benefit of four points in the Semeai Variation.
White will also get the open point at as territory, so her total gain sums up to five points.

Please remember that at that time - before Cheng's improvements - the Semeai Variation was more favourable for Black than the Capture Variation.

Capture Variation:

Black needs two moves to give atari at White's group, as many as in Fujisawa Hideyuki's line of play.

VAR

Black must reduce White's additional gain mentioned above by inserting the upper kikashi in the (temporary) seki as early as possible.

This exchange is Black's priviledge, also explained by Cheng in his 1988 book.

Capture Variation:

Black needs two moves to give atari at White's group, so nothing has changed with regard to the relationship of liberties for the Capture Variation.

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Semeai Variation:

The exchange of for remains White's priviledge, which will be played in the Semeai Variation only.
White will also get the open point at as territory, so her total gain sums up to three points here.

Black's upper kikashi in the hanezeki reduced White's additional territorial gain through Cheng's improvement by two points.

The Semeai Variation will end with Black + 2 now, the same score as for the classical Capture Variation.

Let's return to the amateur analysis room, and compare the world of professionals with that of amateurs ...

Black's territory in the Capture Variation:

Left - Cheng's line of play:

• 34 points for 17 captured White stones
• - 1 point for one captured Black stone

= 33 points in total

Right - After my Second Throw-in

• 36 points for 18 captured White stones
• - 2 points for two captured Black stones

= 34 points in total

Black gained one point by my Second Throw-in, compared to the correct classical solution.

White's territory in the Semeai Variation:

Left - Cheng's line of play:

• 36 points for 18 captured Black stones
• 1 point for territory
• 1 point for one captured Black stone

= 38 points in total

Right - After my Second Throw-in

• 34 points for 17 captured Black stones
• 2 points for two captured Black stones

= 36 points in total

White lost two points by my Second Throw-in, compared to the correct classical solution.

Liberties in the Capture Variation:

With Second Throw-in (at right), Black needs only one move to put White's upper group in the hanezeki in atari, one move less than with the correct classical solution (at left).

However, this seemingly advantage for Black is irrelevant, as Black's large group in the upper right has one more liberty in the classical line of play, so both effects compensate for each other.

Thus, it will remain a mystery what made Fujisawa Hideyuki reject the Second Throw-in.

Let's make a short detour to the dawn of time ...

Referring to Fujisawa Hideyuki's choice , for starting the endgame at the left side, which was analysed in detail in the previous section, ...

... let's try to find out what KataGo thinks about the topic discussed above ...

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We will start our analysis with White's occupation of the Guzumi Point after the termination of the classical Nakade Sequence at the left side.

Please note that KataGo will have exchanged for in the temporary seki much earlier in the game.

: (100 2026)
After the exchange of for , KataGo favours Harry's Hasami-Tsuke , of course.

Playing Fujisawa Hideyuki's classical push with , instead, would be a one-point mistake.

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White exchanges for , as usual.

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After that, however, White immediately connects with .

Continuing with the "usual" attachment at would be mistaken here.
Black would utilise Michael Redmond's Kikashi in the Bamboo Joint, so gaining decisively overall.

Should Black have played Harry's Hasami-Tsuke Sequence earlier (then with instead of ), White would have to exchange the peep for Black's connection before she occupied the Guzumi Point with .

Please note that the reduction of White's upper right corner territory ends in sente for Black, which - according to KataGo - seems to be worth one point overall, compared to Fujisawa Hideyuki's classical sequence.

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Black is forced to follow White with the Main Semeai.

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As a matter of course, KataGo favoured the continuation with Yamada Shinji's Tsuke in the upper left corner.

We manually enforced Fujisawa Hideyuki's Atari .

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This astonishing kikashi in the upper left corner can be often seen in KataGo's games.

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It is best for Black to connect immediately.

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Please remember that Black is unable to connect his pivotal hasami-tsuke stone.

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White erases her remaining weakness in the Guzumi Area.

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White's kikashi fixes the borders at the top.

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White continues the endgame at the left side of the board with the hane at the upper edge.

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

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Black chooses Jérôme Hubert's Solid Connection, as the upper left is already played out.

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Cheng's Bump in the left centre.

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The Man Semeai continues.

Black must not play any reduction.

Capture Variation:

Compared to Our Solution (2015 / 2017), ...

• White's cumulated gain in the upper left corner and at the top is one point.
• White's cumulated gain in the upper left corner is seven points.
• White did not capture Black's stone in the lower left, so losing two points.

In total, Black lost six points.

Black + 5 => White + 1

This is one point better for Black than without my Second Throw-in, as expected.

Semeai Variation:

Compared to Our Solution (2015 / 2017), ...

• White's cumulated gain in the upper left corner and at the top is one point.
• White got an additional four points of territory in the upper right corner, but captured two Black stones less there, so the net effect is zero.
• White did not capture Black's stone in the lower left, so losing two points.

In total, Black gained one point.

Black + 3 => Black + 4

VAR

: ( 2026)
Black plays Fujisawa Hideyuki's Push from the left.

We inserted this move manually.

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Black's descent to the upper edge terminates the reduction sequence.

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We manually enforced Fujisawa Hideyuki's Atari .

As a matter of course, KataGo favoured the continuation with Yamada Shinji's Tsuke in the upper left corner.

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As already mentioned above, KataGo likes to play this surprising kikashi at the left edge.

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It is best for Black to connect immediately.

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White erases one of her remaining weaknesses in the upper right corner.

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Black must follow White with the Main Semeai.

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White continues with the reduction of Black's potential territory in the lower left corner.

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Black defends his lower left corner to the left so avoiding unnecessary complications in the lower left corner.

Playing the atari of at the upper edge or cutting at in the Guzumi Area (quite also considered by KataGo), instead, would not affect the outcome of the game.

White's previous move was played outside the Main Semeai Area, so Black gained one tempo in the Main Semeai.

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White solidifies her formation at the top.

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Black reduces White's potential territory a bit.

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It follows the well-known hane at the upper edge.

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White continues in the Guzumi Area, as "usual".

Please note that Black is par with the Punishment Semeai Liberty Level again, so he will not get any opportunity to exploit White's remaining weakness here.

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Cheng's Bump in the left centre.

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The Main Semeai continues.

Black plays 1/1 reduction.

Capture Variation:

Compared to the superordinate variation, ...

• White got an additional point of territory at the upper edge, but Black destroyed one point of White's territory at the top, so the net effect is zero.
• White captured Black's single stone in the lower left, so gaining two points.
• White got an additional point of territory in the upper right corner, but did not capture Black's hasami-tsuke stone, so the net effect is a gain of one point for Black.

In total, Black lost one point.

White + 1=> White + 2

This is the same overall effect as without my Second Throw-in.

Semeai Variation:

Compared to the superordinate variation, ...

• White got an additional point of territory at the upper edge, but Black destroyed one point of White's territory at the top, so the net effect is zero.
• White captured Black's single stone in the lower left, so gaining two points.
• White got an additional two points of territory in the upper right corner, but did not capture Black's hasami-tsuke stone, so the net effect is zero.
• White captured an additional Black stone in the upper corner, so gaining one point.

In total, Black lost three points.

Black + 4 => Black + 1

2026

2022MainLine