INTERVIEW Korea's nuclear sub plan gains favor in Tokyo amid rising China tensions: Japanese expert
Hirohito Ogi, a senior research fellow at the Institute of Geoeconomics, speaks during an interview with Korean reporters in Tokyo, Nov. 12. Joint Press Corps
Hirohito Ogi points to Beijing as Tokyo's primary security concern
South Korea's plan to acquire nuclear-powered submarines appears to be viewed favorably in Japan, according to a Japanese security analyst who spent 16 years at the defense ministry. The analyst says that the move could help counter China's growing undersea presence and expand security cooperation between Seoul and Tokyo.
Hirohito Ogi, a senior research fellow at the Tokyo-based Institute of Geoeconomics, offered a favorable view regarding South Korea’s pursuit of nuclear submarines, viewing the development as strategically beneficial for Japan.
This public endorsement from a defense analyst in Tokyo highlights a strategic alignment on deterring regional instability, even as South Korea seeks to maintain a cautious balance between its security partnership with Washington and critical economic ties to Beijing.
"I personally think South Korea acquiring nuclear submarines for undersea defense would be a welcome development for Japan. Such capabilities could serve as a counterbalance to China's submarines," Ogi said during an interview with Korean reporters in Tokyo earlier this month.
Seoul's acquisition of such vessels could also open the door to broader South Korea-Japan cooperation in undersea operations, he explained, noting that debate is already underway in Japan about whether it should pursue nuclear-powered submarines of its own.
"If both countries were to have such submarines, joint undersea operations including the United States could become a realistic possibility," he said.
Beijing has emerged as a primary security concern for Tokyo, Ogi said, constituting a shift from several years ago, when North Korea's nuclear threats dominated the agenda.
"China is now the biggest challenge, and North Korea comes second," he said. "This reflects rising concern within Japan about a potential crisis in the Taiwan Strait rather than a contingency on the Korean Peninsula."
Ogi's remarks come as Seoul's long-standing ambition to develop nuclear-powered submarines has gained momentum following recent U.S. approval for uranium enrichment and spent fuel reprocessing — technologies South Korea had previously been barred from accessing.
These developments have drawn swift reactions from neighboring powers.
China has already expressed concern, warning that the move could undermine the global nonproliferation regime under the Nuclear Non-Proliferation Treaty (NPT), while U.S. officials have signaled that the submarines could bolster deterrence against China's expanding influence in the Indo-Pacific.
Ogi said that he took note of President Lee Jae Myung’s public comments on Beijing’s undersea threats, suggesting that shared concerns about China could open the door to closer security cooperation with Tokyo.
During the opening remarks at his October summit with U.S. President Donald Trump, Lee mentioned the limited endurance of South Korea's current diesel-powered submarines, which makes tracking vessels from North Korea or China difficult.
President Lee Jae Myung holds a bilateral meeting with Japanese Prime Minister Sanae Takaichi on the sidelines of the G20 summit in Johannesburg, South Africa, Monday (local time). Joint Press Corps
"I'm not sure how far South Korea's strategic objectives will shift, but the fact that President Lee highlighted the threat posed by Chinese submarines is quite significant for Japan," Ogi said. "It indicates that Japan and Korea are increasingly facing overlapping security challenges in the region."
Seoul has repeatedly stressed that any future nuclear-powered submarine would carry only conventional weapons and that it has no intention of developing its own nuclear arsenal.
Still, the decision has stirred concern among observers who fear it could erode the NPT framework and encourage similar debates in countries such as Japan and Taiwan.
Ogi observed that the debate over nuclear weapons — long considered taboo in Japan — is starting to loosen, amid speculation that Prime Minister Sanae Takaichi might reconsider the country’s longstanding Three Non-Nuclear Principles, which forbid the possession, production and introduction of nuclear arms.
Takaichi’s recent reluctance to clearly affirm whether Japan would continue to uphold the principles has ignited heated debate over the Cabinet’s next steps.
"While it is too early to draw firm conclusions, there is a possibility that the debate inside Japan could shift. In the past, failing to swiftly confirm whether Japan should maintain its Three Non-Nuclear Principles drew critical media coverage," Ogi said. "But the notion that nuclear issues are off-limits appears to have softened. Still, public understanding about nuclear weapons has not deepened yet."