North Korea's leader Kim Jong-un should pay damages for a 1959-84 scheme that saw more than 90,000 people move there from Japan, a Tokyo court is hearing, reports BBC.
The repatriation campaign was later condemned by some as "state kidnapping".
They do not expect Mr Kim either to appear or to pay up, but hope a ruling may help in future negotiations.
Thousands of Koreans moved to Japan - many against their will - during its colonial rule of the Korean peninsula from 1910 to 1945. The vast majority of people involved in the resettlement scheme were ethnic Koreans being sold a vision of the "Fatherland" as "paradise" - and some Japanese spouses went with them.
Both North Korea and Japan supported the campaign.