Source: 
Problem diagram.
Black's response to the marked stone?
Kato Masao (as a 12 year old) vs. Kitani Minoru 9 dan (Kato's teacher)
Analysis: Kato (as a 9 dan)
Solution follows
(or click here to download SGF)
Best.
Black 1 is a simple and classic attacking move,
but the strong 12 year old Kato missed it.
Then Black 3 would efficiently coordinate all his stones.
Note the perfect placement of even the handicap center stone.
The White group's prospects would have been dim.
A mistake.
Black 1 is the game line, but a mistake in direction.
Making the triangular shape here is good locally,
but slack for attacking the White group above.
White is happy to jump out with 2.
Black should then have played at the top with 3 here, but didn't.
Then Black could have still balanced the attack of the
White group below with the defense of his top group.
After 5, Black is not as good as the best line in the previous diagram,
but Black is still better than the game line in the next diagram.
The full game line.
Black 3 is also the game line, and again in the wrong direction.
Black was trying to make use of the center handicap stone.
After White 4, now Black's group is in danger.
Through 8, White's group is much stronger.
Compare this position with the 2 diagrams above.
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