: ( 58ap)
White plays the hasami-tsuke in the lower left corner, which is part of the endgame.

This move will increase the susceptibility to errors in the following course of the game unnecessarily (and can be a genuine mistake; 58by), and so can be considered to be a technical mistake in the timing of moves.

: (A 58dd)
Black gives atari immediately.

Playing tenuki to the large hiki at the top, instead, would be a grave mistake. Due to his remaining weaknesses at the left side of the board, Black would lose the game decisively.

The development of the somewhat "delicate" position below is possible only after White's exchange of for . White should refrain from playing this exchange, if she does not want to continue locally immediately thereafter.
This implies that she should wait with starting the endgame sequence in the lower left corner until Black has decided about the line of play after White's crosscut in the upper left corner.

:
White captures Black's single stone in the lower left, so continuing with the Main Semeai.

:
Black blocks, as usual.

:
KataGo often chooses this move to give atari at Black's nakade stones.

:
Black gives atari at White's two stones in the lower left at the earliest possible moment.

:
White inserts the crosscut at the top, reverting to the "usual" sequence after Yamada Shinji's tsuke.

However, as we will see below, there is no guarantee to deliver a flawless game thereafter.

:
Black has to give atari from the inside.

:
White captures the nakade "early".

:
White connects her two stones in the lower left, so losing two tempi in the Main Semeai.

(Referenced by 58ct)

:
KataGo likes to play this guzumi in the left centre now and then. This new move - played instead of the usual one at - also defends against White's threats of and .

Please note that his move provides White with an unexpected (and new) opportunity for destroying Black's potential territory in the left centre, but which is poisoned, as we will see below.

Please also note that this move is not a mistake here, despite it is played after White connected her two stones in the lower left with her previous move.

Contrary to a comparable earlier subvariation ( 58ct), Black has already played the inside atari after White's crosscut in the upper left corner.

:
White continues with the Main Semeai.

:
White inserts a kikashi at the top.

:
The Nakade Sequence is finished now.

:
White returns to the still unfinished position in the upper left corner.

(Referenced by 58aa)

: ( A 58dg)
Black defends his lower left corner, instead of blocking with at the upper edge.

This alternative option is not better overall than the "usual" defense of the upper left corner (Black will be worse by four points in the Semeai Variation here, correct continuation assumed), but at least more confusing for KataGo, as it seems.

: (121 58dh)
White forces at the fourth line.

I would have expected White to push at the bottom line, instead, not affecting the final scores of the game.
This alternative option would, however, still allow the mutual reduction of opponent's territories, which will become the deeper source of KataGo's later mistake here.

Please remember that the marked exchange in the lower left corner was played before its time, making the position more "delicate" than necessary.

:
Black descends to the bottom.

: (A 58dj)
White gives atari in the upper left corner.

Connecting her single stone in the right centre, instead, would come too early.

:
White inserts a kikashi in the centre.

:
White returns to reducing Black's corner territory.

:
KataGo seems to like jumping back and forth.

:
Black has to capture White's single stone in the right centre.

:
White captures two Black stones in the upper left.

:
Black recaptures.

: (A 58dm)
White plays another kikashi in the lower left corner.

It would not affect the overall result of the game, if White did without this move, or played this atari later.

:
Black has to capture.

Please notice the (not very obvious) destructive impact of White's earlier played kikashi , on the power of her potential territory-reducing moves from the left (starting with ).
Without this exchange played, Black would have to immobilise by giving atari from below, but which would remain on the board. A positive side effect for White would be that her move at would not hit a dead end, as it will do here.

: ( A 58do)
White's push into Black's potential territory in the left centre is the game-deciding mistake in this selfplay game.
With the current position in the lower left corner, White must never ever start with the mutual reduction of opponent's territory. However, even the newest Katao net from end of July 2021 does not "see" the correct continuation.

White must continue with the Main Semeai, instead.

:
Black blocks.

Please note that Black just won an additional tempo in the Main Semeai, which brings him to two over par, related to the Punishment Semeai Liberty Level.

:
White's bump in the left centre stops Black from playing or successfully.

; : (149 58dq)
White destroys two points of Black's territory at the cost of two tempi in the Main Semeai.

Allowing Black's forthcoming push at is quite unususal. However, it would not make a difference if White prevented this move.

:
Black destroys one point of White's territory at the cost of one tempo in the Main Semeai.

Hereafter, Black is three over par, related to the Punishment Semeai Liberty Level. This implies that he has sufficient room for actions.

White needed five moves () to prevent all of Black moves that would reduce her territory at the top or in the upper right corner.

Black needed only three moves () to defend against all White moves that would reduce his territory in the upper left and lower left corners.

Therefore, a White strategy of defending weak points would not lead to success, as she has more weaknesses to cover than Black (even if we take her sente into account).

Please note that White cannot stop Black from connecting his single stone in the lower right, should this become necessary.

A strategy of playing all destructive moves first does not make sense for White here, either, as Black has sufficient means for compensation again.

White has already played three reductions, Black one.

White could still play three reductions ().

Currently, Black is three over par with the Punishment Semeai Level, so he could play six reductions (; connecting counts as two) thereafter. Black would be able to compensate at the right for what he lost at the left, and still keep the three surplus reductions alive, which he needs for success.

Black plays 3/3 reductions.

Capture Variation:

Compared to the superordinate variation, ...

• White's cumulated gain in the upper left corner, and at the top, is eight points.
• White destroyed three points of Black's territory in the left centre.
• Black's cumulated gain in the lower left corner is five points.
• Black did not capture White's two stones in the lower left, so losing four points.
• Black captured White's stone in the right centre, so gaining two points.
• White did not capture Black's stone in the lower right, so losing two points.
• Black destroyed an additional three points of territory at the right.

In total, White gained three points.

Black + 2 => White + 1

Semeai Variation:

Compared to the superordinate variation, ...

• White's cumulated gain in the upper left corner, and at the top, is eight points.
• White destroyed two points of Black's territory in the left centre.
• Black's cumulated gain in the lower left corner is five points.
• Black captured four White stones more at the left, so gaining seven points.
• White captured four Black stones more at the right, so gaining six points.
• Black destroyed one point if White's territory in the upper right corner.

In total, White gained three points.

Black + 2 => White + 1