Obara beat Mariya Stadnyk to claim the first gold in the women's Wrestling at London 2012, defeating the Azerbaijani 0-4 1-0 2-0 in a thrilling fight played out in front of a raucous Japanese following.
Obara, 31, had retired twice from the sport after failing to make Japan's Olympic team at the last two Games but opted to return.
Stadnyk looked set to cause a huge upset when she strolled to victory in the first period, but the Japanese used all her experience to get behind her opponent and win the second before pushing her off the mat in the third.
Icho beat Jing Ruixue to claim her third successive Olympic gold. She went out all guns blazing, throwing Jing in the first period before manoeuvring behind the silver medallist in the second to clinch victory.
She became the only woman wrestler to triumph in Athens, Beijing and London after she outclassed her Chinese opponent to record a straightforward 3-0 2-0 win.
In the 48kg category, Clarissa Chun came through the repechage to win bronze - the USA's first Wrestling medal of the Olympics.