: ( 648qa)
White pushes into the corner.

Ko: ; ; ; ;

:
Black connects, also creating an eye.

Ignoring White's previous move is out of the question, as White would turn his upper left corner into a seki. For details, please refer to an older subvariation ( 648nf). Please note that there the order of White's first two moves in the corner is interchanged.

: ( A 648qd)
Black continues with the ko fight by playing one of his ko threats in the upper right.

KataGo (2021i) favours the connection in the right centre just now, which implies that KataGo (2021i) wants to play this move as early as possible.

: (167 648qe)
White's plays her next ko threat in the upper left corner.

KataGo (2021i) favours a move at , instead, which will allow White to generate yet another ko threat in the upper left corner. Nevertheless, the outcome of the ko fight here will not be affected, as White is already ahead in valid ko threats.

: (162 648qk)
Black's response at the upper 1-2-point deprives White of any options in the corner.

Again, Black is unable to ignore White's previous move, instead. If he really did, his entire corner would be turned into a seki.

: ( A 648qm)
Black peeps in the right centre.

However, this is the last moment, when Black can play the connection at in the right centre, in order to benefit in the Semeai Variation.

:
This atari is White's fourth ko threat in the upper left.

:
As a matter of course, Black has to connect.

: (A 648qn)
Black plays his last territory-reducing (in the Capture Variation) ko threat in the upper right corner.

Connecting at in the right centre, instead, will not affect the final scores of the game. This window of opportunity has closed.

Ko: ;

; :
Please understand these two moves as replacement for White's kikashi , in the centre, which had been played too early by us.

:
Black connects in the upper right, intending to establish some points of territory there. However, this move comes too late now to be effective.

:
White pushes from above

:
Black recaptures the ko.

Alternatively, he might consider capturing with immediately.

:
White plays her very last ko threat.

Connecting her stone in the upper right with , instead, will be mistaken, similar to the case when White plays as a ko threat ( 648qt; please note that White's different play in the upper left corner does not matter).
If she did, Black would win the Semeai Variation.

: (A 648qo)
Black captures White's stone in the upper right, as he does not have any viable ko threats left.

Black might want to give Joachim's idea of throwing-in at in the guzumi area a try. White, however, will benefit by one point overall - if she stays calm enough to find the correct counter.

:
White has to connect the ko - sooner or later.

Black plays 0/2 reductions.

After White's kikashi in the lower left corner, Black will have to capture at before the end of the game.

Capture Variation:

Compared to the superordinate variation ...

• The cumulated effect of White's different play in the upper left corner is zero.
• Black did not destroy one point of White's territory at the upper edge.
• Black got an additional point of territory in the right centre.

In total, gains and losses compensate for each other.

White + 2 => White + 2

Semeai Variation:

Compared to the superordinate variation ...

• The cumulated effect of White's different play in the upper left corner is zero.
• White captured one Black stone less at the upper edge, but one stone more in the right centre, so the net effect is zero.

In total, gains and losses compensate for each other.

White + 2 => White + 2