The country’s Yomiuri daily claimed that Chief Cabinet Secretary, Yoshihide Suga, said Japan is using “every means” to explore how people can be evacuated in the event airports are closed in the South.
He said: “It’s a totally natural duty as a nation to use every means at our disposal for the protection and evacuation of our citizens if they should face danger abroad.”
The report claimed that military ships would be used as shuttles to rescue citizens via the southern port city of Busan.
Once the vessels have been boarded, residents would then be taken to Japan’s Tsushima island – roughly halfway between the two nations.
A day or two later, the ships would then arrive in the country’s southern island of Kyushu.
Government officials have visited hotels in Tsushima to inspect hotels and other places of residence that citizens could stay.
The paper also detailed that supplies of food and water are being planned for.
The report comes ahead of South Korea’s PyeongChang Olympic Games next month.
North Korea has appeared eager to engage in dialogue with its neighbour as the event approaches.
On January 9 North and South Korea held talks at a ministerial level for the first time since December 2015.
The countries are even discussing fielding a joint women’s hockey team at the games.
But the Rodong Sinmun, the official newspaper of Kim Jong-un’s despotic regime, has claimed Washington is “preparing to deploy its strategic military assets around the Korean Peninsula”.
It said: “The US is repeating its pledge not to ease sanctions and pressure until the North abandons nuclear and ballistic missile programs.
“It is throwing cold water on an atmosphere of reconciliation.”
South Korea and the US have agreed to postpone the annual military drills Foal Eagle and Key Resolve that infuriate North Korea.
PyeongChang 2018 will run from February 9 to February 25.