Korean victims of Japan's wartime sexual slavery have called for "righteous judgment" ahead of an expected court ruling in the victims' second damages suit against the Japanese government.

At a press conference on Monday, groups assisting the victims said they firmly believe that the Seoul Central District Court will make a just ruling on April 21 that aims to restore the victims' dignity and honor.

The latest suit was filed in 2016 by 20 victims and family members, marking the one-year anniversary of a bilateral agreement on settling the so-called comfort women issue.

While Japan has refused to comply with court proceedings, citing sovereign immunity, two of the victims, including the late Kim Bok-dong, have died.

At the press conference, the groups stressed that sovereign immunity can be restricted for serious crimes that violate the peremptory norm, such as Imperial Japan's planned and systematic sexual enslavement during World War Two.

In January, the same court dismissed sovereign immunity, but sided with the victims in ordering Tokyo to pay monetary compensation.