Tetsuya Yokota, one of twin sons and brother to Megumi, said at a press conference the North Korean leader has yet to resolve the issue of abducted Japanese citizens to North Korea, NHK and Sankei Shimbun reported.
"I think [Kim Jong Un] is a foolish leader," Tetsuya Yokota said.
Tetsuya and his twin brother, Takuya, are activists who have been at the forefront of the abduction issue, along with their mother Sakie Yokota. Japanese Prime Minister Shinzo Abe said last year the kidnappings of Japanese citizens is a top priority, but Tokyo has made little progress on the issue.
Megumi was abducted to North Korea as a teenager. She was 13 when she vanished from her hometown in Niigata Prefecture in 1977. Shigeru Yokota at the time was an employee of the Bank of Japan and was never able to reunite with his daughter before he died last week at age 87.
On Tuesday, Tetsuya Yokota said among the Japanese families of kidnapping victims, there are "elderly people, whose health is not good."
"We hope there are concrete results in order to prevent the same things from happening again," he said in his message to the Japanese government.
"Father deeply cherished our sister," Takuya Yokota said. "It is unbearable to think of how much he wanted to see her."
North Korea confirmed Megumi was abducted and married Kim Young-nam, a South Korean abductee.
The two victims of North Korea's secret program of kidnappings had a daughter together. Pyongyang later told Tokyo Megumi struggled with depression and died by suicide in April 1994.
The Yokotas never accepted the North Korean claim. In November 2004, North Korea delivered to Japan what it claimed were Megumi's remains, but a DNA analysis found them to be that of someone else.