A military-intelligence sharing deal, which has been in the pipeline for five years, will allow both countries to share information directly without using the US military as an intermediary.
Washington, a close ally of both countries, has long encouraged better relations between the two even though many in South Korea are critical of the pact.
South Korea’s Ministry of Defense in a statement Wednesday highlighted the merits of the deal, saying “Japan’s investment in national defense is higher than South Korea’s which enables the country to monitor and detect military information.”
Seoul is hoping the data will help it to analyze North Korea’s ballistic missile launches and their trajectory as well as the country’s nuclear and submarine capabilities.
The deal comes amid uncertainty over the future of the THAAD missile defense system, which Seoul and Washington agreed to deploy in South Korea by the end of this year.
Japan is the 33rd country South Korea has signed a military deal with. Under the agreement, which takes place immediately, all confidential and secret information can be shared between the countries’ intelligence agencies. Top secret information is not covered by the deal.
The intelligence-sharing pact has plenty of critics in South Korea.
Japan occupied Korea for 35 years before the end of World War II, and anti-Japanese sentiment still lingers.
Last year, a deal was struck between the two governments over the long-standing issue of Korean sex slaves used by the Japanese military during the war.
Advocacy groups for the so-called “comfort women” slammed that agreement as a “diplomatic humiliation.”
Hundreds of thousands of people have taken to the streets in recent weeks calling for Park’s resignation, while prosecutors named her as a suspect in an ongoing corruption investigation Sunday.
“The Park administration has already lost its legitimacy so she should immediately take her hands off (national affairs),” Lee Jae-jeong, spokeswoman for the Minjoo opposition party said in a statement.
CNN’s James Griffiths contributed reporting.