: ( 648of)
White throws-in in the lower left corner.

This throw-in generated an approach-move liberty for her group.

:
Black captures two White stones in the lower left.

: (C 648oh; A 648oj; B 648ok)
White continues with the Main Semeai, hoping that Black will fall into a trap that is explained below.

She might also block at the top with , or play Dany's atekomi in the centre, achieving the same final scores as herein.
Connecting her single stone at the upper edge with , however, will be worse for her.

:
Black plays his remaining kikashi in the hanezeki.

:

Black is par with the Punishment Semeai Liberty Level, so pushing with at the top (expecting White to answer at ) would be a grave mistake, but which is not necessarily very obvious. Please refer to ( 648ap) for details.
Please understand the exchange of and at the lower edge as a means that allowed us to keep the move numbers in many of the following diagrams stable, after we deleted our hitherto existing moves at and here.

:
Black continues with the Main Semeai.

At this moment, with the open points lA and lB (and lC), it might be difficult to decide what else might be possible for Black.
I made several mistakes while creating the first version of the diagrams for the subvariations (as a matter of course, without colour-coded borders), because I took matters for granted that really were not.
Especially for amateurs, I would like to recommend the following procedure to get a better basis for the evaluation of the current board position and its interdependencies.

Play ONLY moves that are part of the Main Semeai, until you reach White's decision point.

:
White might consider giving atari at just now - not affecting the final scores - but here, we will wait with this move until after her decision point.
Please remember that Black is bound to moves that are part of the Main Semeai, so in the left centre, or (and ) at the top, are currently out of the question.

...

:
We have reached White's decision point, where White's group on the left side has only two liberties left. Next, Black would give atari with , and White would capture at .

However, this is the moment to identify the number of liberties of Black's large group in the upper right. This will be the basis for considerations about moves especially on the left half of the board, where several spots are still open.

Black's group in the upper right has six direct liberties (), and one approach-move liberty (), due to Black's eye.

In total, Black's group has seven liberties.

This is barely enough to survive the Punishment Semeai.
Therefore, Black does not have any liberty to spend, which would be the case if he played an additional gote move, like the connection at in the centre, or the capture of one White stone at the upper edge with .
On the other hand, even White has to be on her guard. It might be tempting, to connect at , after Black connected in the centre with . But White would give up her success with the Punishment Semeai.

:
The game continues.

Capture Variation:

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White captures the hanezeki's tail.

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Black has to recapture.

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The usual course continues with Joachim's Oki.

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After the resolving of the hanezeki in the lower right, White has sente to give atari in the left centre.

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The areas at the upper edge, and in the centre, are miai.

White could also play at in the centre, letting Black capture at . The final scores would remain unchanged.

:

Now, after White lost one tempo in the Main Semeai, the time has come for Black's push at the top.

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Eventually, Black erases White's potential territory in the left centre.

... :
In the "normal" course of the sequence, White would have played these moves much earlier, and left neutral points unoccupied, instead.
This implies that Black must not play at any of these points (reducing White's territory) in this phase of the game - which has to be understood as following a "fictive" sequence, for better analysis only.

:
Black plays the last move on the board.

Please note that this might be necessary to ensure SGF editors to calculate the final score correct, when using (or being based on) area scoring (i.e. Chinese counting).
In the starting position of the problem, White has one more stone on the board as Black, so Black has to make the last move to even the count of played stones. This seems to be independent of the specification of komi.

Compared to the superordinate variation ...

• White's cumulated gain at the upper edge is two points.
>
• Black did not get any territory in the centre, so losing one point.
• Black captured White's two stones in the lower left, so gaining four points.

In total, White lost one point.

White + 2 => White + 1

///:

Semeai Variation:

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White can start the Semeai Variation with the atari in the centre.

:

Again, Black is able to play the push at the top, after White lost one tempo in the Main Semeai by her connection at .

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This is the start of the "proper" Semeai Variation, taking Black's seventh liberty in the upper right.

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Black has to connect the hanezeki's tail.

...

...

:
Again, Black has the last move on the board.

Compared to the superordinate variation ...

• White's cumulated gain at the upper edge is two points.
• Black did not get any territory in the centre, so losing one point.
• Black captured one White stone less in the lower left, so losing two points.

In total, White gained five points.

Black + 4 => White + 1