Japanese government sources say a professor from Hokkaido University has been freed from detention in China and returned home on Friday.
The professor, who is in his 40s and specializes in modern Chinese history, was detained in September while visiting Beijing at the invitation of the Chinese Academy of Social Sciences.
China's Foreign Ministry also disclosed the professor's release on Friday.
The case raised concern among Japanese experts on China, prompting some to cancel their trips to the country.
Earlier this month, Prime Minister Shinzo Abe requested the professor's early release when he met Chinese Premier Li Keqiang on the sidelines of a regional forum in Thailand.
Li said that he had taken note of Abe's request.