The incident occurred in early January near Beijing, when the woman allegedly took a picture of the man exposing his buttocks at the world heritage site, Japan Today reported on Thursday citing a Japanese government source.
Local security officials detained the couple on the spot for two weeks before deporting them back to Japan.
The incident has already sparked outrage in Japan, a country known for its emphasis on politeness and respect for laws.
"As a Japanese person, this is shameful," one netizen commented on Japanese outlet Nihon Television News.
"If Japanese people embarrass themselves like this overseas, it will damage the reputation of our entire nation," the netizen added.
Another user wrote on Japan Today that "Incidents like this highlight how much Japan has declined morally, educationally, and socially over the past couple of decades."
"You should obey the rules in foreign countries," another wrote.
"I have been to China and I would never do that," another commented.
Some Japanese netizens argued that the punishment was too lenient, with one stating, "It's disgraceful for these two tourists to behave this way at a historical site, two weeks’ detention is too light," according to Global Times.
In November last year, China reinstated its unilateral visa-free policy for short-term Japanese visitors, allowing stays of up to 30 days. The policy will remain in effect until the end of 2025.