White was ahead but I don't think that this is easy to see. However, after making some timesuji like move Shibano, who is white, seemed to have a blind spot and played something that didn't work out. So in the end it was Yamashita that won.
You can have a Go at finding the right move.
$$W White to play.
$$ +--------------------------------------+
$$ | . . . . O X X . . . . . . . . . . . .|
$$ | . . . . O O X . . . . X . . O O O O .|
$$ | . . . . X O . X . 1 X . O O X O . . O|
$$ | . . . O O O X X X 2 O . O X X X O O .|
$$ | . O O . . X O X O O . X X X . . X X .|
$$ | . O X X . . O X X O . . O O O X X . .|
$$ | . . . . . O X X X O . O . . X . . . .|
$$ | . . . . . X O O O O O X X . . . . . .|
$$ | . . . X X X O . O X X . . X . . . . .|
$$ | . . X X O O . O O , O X . X . , . X .|
$$ | . X O X X O O O X O . X X X X O X X O|
$$ | . O O X O X X X X X X X . X O X X O .|
$$ | . . O X O O X . . O O O O O O . O . O|
$$ | . . O . O X X . O O X X O . O . O O .|
$$ | . . . . O X . X . . . . . O . X . . .|
$$ | . O O O X O O . O O X X . . . X . O .|
$$ | . O X X X X O O O . O X . X . X O . .|
$$ | O X . . X . X O X O O O X . . . X X .|
$$ | . X . . . . 4 X X 3 . X . . . . . . .|
$$ +--------------------------------------+
- Click Here To Show Diagram Code
[go]$$W White to play. $$ +--------------------------------------+ $$ | . . . . O X X . . . . . . . . . . . .| $$ | . . . . O O X . . . . X . . O O O O .| $$ | . . . . X O . X . 1 X . O O X O . . O| $$ | . . . O O O X X X 2 O . O X X X O O .| $$ | . O O . . X O X O O . X X X . . X X .| $$ | . O X X . . O X X O . . O O O X X . .| $$ | . . . . . O X X X O . O . . X . . . .| $$ | . . . . . X O O O O O X X . . . . . .| $$ | . . . X X X O . O X X . . X . . . . .| $$ | . . X X O O . O O , O X . X . , . X .| $$ | . X O X X O O O X O . X X X X O X X O| $$ | . O O X O X X X X X X X . X O X X O .| $$ | . . O X O O X . . O O O O O O . O . O| $$ | . . O . O X X . O O X X O . O . O O .| $$ | . . . . O X . X . . . . . O . X . . .| $$ | . O O O X O O . O O X X . . . X . O .| $$ | . O X X X X O O O . O X . X . X O . .| $$ | O X . . X . X O X O O O X . . . X X .| $$ | . X . . . . 4 X X 3 . X . . . . . . .| $$ +--------------------------------------+[/go]
Hints:
First it is more of a tesuji problem, you can try to find the only move that works for white, and you can probably be happy with that. If you have the right move then there is the second problem which is an endgame problem, how to make use of it given that black won't self-destruct. Maybe just solving the first one is good enough, there isn't a definite end to the second problem but there is some point to solving the first tesuji problem.
Shortage of liberties ahoy!
Think of the suji of the diagonal move. If you can guess the move you can probably work it out from there.