North Korea's abduction of Japanese citizens in the 1970s and 1980s continues to sour relations between them. The BBC's Chris Hogg meets the Japanese who still pursue the truth about their loved ones.
For those who suspect their relatives were among the men, women and children snatched by North Korea to train their spies, this issue is much more than just a diplomatic hurdle.
It is an unsolved crime that has continues to cause deep distress to hundreds of Japanese families.
Every day a shortwave radio programme broadcast from Tokyo highlights the plight of those who were kidnapped.
It is compiled in a small booth in an office owned by a group which campaigns to keep the issue in the public eye and supports the families of those abducted.
JSR Shiokaze radio is broadcast once in the morning, once in the evening for 30 minutes.
There are editions in Japanese, Korean, English and Chinese, rotated on a regular basis.
It includes the latest news about the abduction issue, messages to those abducted and appeals for help in finding them.
'Overwhelming emotion'
Shigeo Iizuka, an elderly man dressed in a smart suit, has come in to record a message to his sister. He believes she was taken by North Korean agents almost 30 years ago.
Mr Iizuka campaigns tirelessly for Pyongyang to resolve the issue.
He goes into the booth and once he gets the signal from the programme director he starts to read his message.
Programme director Kenji Murao explains that for many relatives it is an emotional experience to reach out like this over the airwaves.
"Most people cry," he says. "A lot cannot speak because they are so overwhelmed, so they write a letter and ask us to read it."
Mr Iizuka maintains his composure throughout the recording.
Afterwards he says it is hard for anyone to understand how the families of the abductees feel.
"Family is the starting point for everything," he says. "The fact that members of our families have been abducted makes us angry."
He points out that "the victims of this crime" are stuck in a country where there is such poverty they may not have proper heating in winter, or enough food.
"My sister was 22 when she was taken there. She will be 51 this year," he says.
"We will do everything we can to get our relatives back. Some of us have been waiting more than 30 years."
No Pyongyang deals
Japan's government recognises officially just eight men and nine women as having been abducted.
These are the cases they feel they have enough evidence to prove beyond doubt.
North Korea has admitted abducting just 13. It returned five to Japan but said the others were dead.
It is believed that some younger victims were taken to teach Japanese language and culture in North Korean spy schools.
Older victims may have been abducted so that their identities could have been used by spies.
Some think it is more likely that they were killed immediately.
Mr Iizuka says his group will continue to do all it can to keep the issue in the public eye and to keep up the pressure on North Korea.
"As long as we can tell others that North Korea is a terrorist nation, I don't think people will help them," he says.
He opposes any suggestion that Japan should provide financial aid to North Korea as part of a future denuclearisation deal, unless the abduction issue has been resolved first.
On a poster behind Mr Iizuka are the faces of the many Japanese whose relatives believe are abductees.
Many of the pictures are very old - a reminder that this is a struggle the families have been involved in for decades.
"These were my sister's most precious years," Mr Iizuka says, describing the time she has spent in North Korea.
For him, and for the others whose messages are broadcast each day, the loss of that time spent with family members is a crime that cannot be ignored.
