The incident led the military to institute a curfew for U.S. military personnel in Japan, Stars and Stripes reported.
The victim was walking home from work on the morning of Oct. 16, the prosecution said, and ignored the two sailors when they tried to talk to her.
In changing their pleas in mid-trial, Christopher Browning, 24, and Skyler Dozierwalker, 23, admitted they attacked and carried the victim to a parking lot, where they raped her for nearly an hour, the newspaper said.
Browning also took $87 from her bag.
The assault was captured on security cameras and was shown to the jury Tuesday, Start and Stripes said.
The Naha District Court is to issue the final sentences Friday.
The victim wasn't in court but her written statement was read to the jury.
"The pain in my neck and throat will go away some day, but the pain, humiliation and despair that I experienced will never go away," the statement reads.