Tomoe Terakoshi left the port of Niigata aboard a freighter Wednesday to see her son, Takeshi, who has been living in Pyongyang since he and his uncle disappeared while fishing in the Sea of Japan in May 1963.
During her 15th trip to North Korea, Terakoshi will also meet her husband, who moved in with Takeshi and his family last year.
Terakoshi last visited North Korea to see her son, who told Japanese officials Monday in Pyongyang that he hopes to make his first visit back to Japan, in May 2001.
She plans to return to Japan Sept. 2 after her stop in Pyongyang and a visit to Panmunjom, the truce village in the demilitarized zone between North and South Korea.
Terakoshi learned her son was alive in 1987 through a letter she received from her brother, who also ended up in North Korea. She has since been lobbying the Foreign Ministry in Tokyo to persuade North Korea to allow him to visit Japan.
Last year, her husband moved to Pyongyang to be with their son.
In Pyongyang on Monday, Takeshi Terakoshi told reporters, "I plan to return home." He also told senior officials of the Japanese Red Cross Society and the Foreign Ministry of his plan during a meeting earlier in the day at a Pyongyang hotel.
Takeshi said through the North Korean media in 1997 that the boat from which he and his uncle had been fishing was wrecked at sea and that a North Korean fishing boat had rescued them.
The two men later acquired North Korean citizenship. The uncle died in North Korea.