She beat Mariya Stadnyk of Azerbaijan to add the Olympic 48kg title to the eight world championships she has won in a dazzling career.
Obara fell to her knees on the wrestling mat and wept with her head in her hands as Japanese supporters erupted in the packed arena. Obara lost the first of three rounds, but fought back to win the next two.
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The pair had also met in last year's world championship final, a closely fought contest that Obara also won.
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