Koichiro Iizuka was 12 months old when his mother, Yaeko Taguchi, was abducted by North Korean agents.

She was 22 when she disappeared after dropping him and his three-year-old sister at a day care centre in Tokyo in June 1978.

He says he was too young to remember his mother's warmth, the sound of her voice, or her smell.

The children were raised by their mother's siblings and didn't learn the extraordinary story about her abduction until they were adults.

Ms Taguchi's disappearance had been treated as a simple missing person's case — and with little evidence about what had happened to her, the police investigation ran cold.

But when a South Korean passenger jet travelling from Baghdad to Seoul was bombed in 1987, the investigation revealed a critical piece of information for Ms Taguchi's family and her children.

The North Korean agents who bombed the plane had been posing as Japanese tourists.

The bombers had placed the device on the plane and disembarked. And one of them later told investigators she'd been taught Japanese in North Korea by Ms Taguchi.

Mr IIzuka says it was only when he applied for a passport as an adult that he learned the full story.

"I was told a woman who I've never met was my mother, so I was very shocked," he said.

"On top of that she'd been abducted to North Korea. I couldn't digest the information. I remember having an inexpressible feeling."

Since then, he's been trying to shine the spotlight on the issue of North Korean abductees.

He is a member of a group that will meet the US President Donald Trump in Tokyo today.

His mother is one of 13 Japanese people that Pyongyang has admitted to kidnapping. Many suspect there are many more unexplained missing persons cases in Japan which could be linked.

Mr IIzuka says he was pleased when Mr Trump drew world attention to the issue of North Korean abductions when he spoke recently at the United Nations.

The President talked about the case of Megumi Yokota, the most high-profile of Japan's abduction cases.

Shigeru Yokota shows a photo of his daughter Megumi, who was kidnapped by North Korea when she was 13. ( Reuters: Eriko Sugita )

She was 13 when she was taken while walking home from school.

North Korea has admitted to kidnapping her, but says she has since died.

"[Mr Trump] has said that the abduction issue is the most important issue for Japan so I'd like him to tell Kim Jong-un that nothing will start unless this issue is resolved and they have to return all the victims back to Japan," Mr IIzuka said.

Japan's Prime Minister Shinzo Abe has long been a campaigner for the issue and says he's asked Mr Trump to meet the families during this trip to Asia.