Why South Korea Is Wrong to Treat the Sino-Japanese Clash as Someone Else’s Problem

The recent surge in tensions between China and Japan, triggered by Prime Minister Sanae Takaichi’s remarks in the Japanese Diet, has been widely followed in Seoul with a sense of detachment. For many in South Korea, the episode appears to be little more than a bilateral dispute—an external confrontation with limited bearing on the Korean Peninsula.

This perception is not merely complacent; it is strategically flawed. The current Sino-Japanese confrontation is unfolding not during a period of international stability, but amid a systemic transition in the global order. Its trajectory is likely to shape the security environment surrounding the Korean Peninsula in ways that South Korea can ill afford to ignore.

The immediate catalyst was Prime Minister Takaichi’s statement during a House of Representatives budget session on November 7, 2025. Responding to a question about Taiwan, she stated that a Chinese military operation against the island could constitute an “existential threat” to Japan, and that Tokyo might respond through the exercise of collective self-defense. Rarely has a Japanese leader spoken so explicitly about potential military involvement in a Taiwan contingency.

The legal foundation for her remark dates back to 2014, when the second Abe administration reinterpreted Japan’s postwar security framework. Facing China’s rapid military expansion and North Korea’s advancing nuclear capabilities, Tokyo sought to ease the constraints imposed by Article 9 of the constitution. While formal constitutional revision proved politically unattainable, Japan established a legal category—“situations threatening Japan’s survival”—under which limited collective self-defense could be exercised if an attack on a closely related state endangered Japan itself.

Crucially, this framework was designed to remain deliberately ambiguous. Successive prime ministers avoided specifying concrete scenarios in which it would apply, preferring strategic vagueness to political risk. Takaichi’s remarks therefore represented a departure from long-standing restraint, signaling a willingness to define Taiwan explicitly within Japan’s security perimeter.

Beijing’s response was swift and uncompromising. A senior Chinese diplomat in Osaka employed inflammatory language that ignited public outrage in Japan, while Beijing advised its citizens to avoid travel and study there. Cultural exchanges were suspended, air routes were reduced, and Japanese seafood imports—only recently resumed—were once again halted. The deterioration soon extended into the military domain, with China deploying large numbers of naval and coast guard vessels and reportedly locking radar onto Japanese aircraft.

These developments are not the product of momentary diplomatic miscalculation. They reflect deeper structural forces now reshaping East Asia.

First, China’s reaction must be understood within its broader challenge to the postwar regional order. Beijing has increasingly questioned the legitimacy of the San Francisco Peace Treaty framework, asserting that Taiwan is territory Japan was defeated and therefore obligated to return. In this context, Takaichi’s remarks were readily incorporated into China’s domestic narrative on sovereignty and historical justice—an arena in which compromise is politically inconceivable for the Xi administration.

Second, Takaichi’s refusal to retreat cannot be explained solely by personal ideology. Japanese public opinion has shifted markedly over the past decade, shaped by repeated confrontations over the Senkaku Islands and a growing perception of strategic vulnerability. Within Japan’s political landscape, a firm stance toward China now carries electoral advantage rather than cost. The erosion of pro-China factions within the ruling Liberal Democratic Party, combined with the departure of Komeito—a traditional conduit for Sino-Japanese dialogue—from the governing coalition, has further narrowed Tokyo’s diplomatic room for maneuver.

This bilateral confrontation is unfolding against the backdrop of a larger transformation in U.S.–China relations and the international system itself. That transformation carries three critical implications for the Korean Peninsula.

First, the crisis highlights the gradual hollowing-out of the Indo-Pacific framework designed to constrain China. The second Trump administration’s National Security Strategy places rhetorical emphasis on Taiwan while adopting a noticeably restrained tone on China’s military threat. It reiterates President Trump’s long-standing skepticism toward alliances, framing them as transactional arrangements rather than strategic commitments. Notably, Washington has offered no clear political backing for Takaichi’s position.

This signals a broader erosion of the U.S.-led liberal international order beyond the economic realm. As the United States increasingly prioritizes the Western Hemisphere and reduces its normative commitments elsewhere, global politics is reverting to a system driven less by rules than by raw power. In such an environment, the preferences of great powers—particularly the United States, China, and Russia—will outweigh the agency of middle powers like South Korea. Seoul must prepare for a future in which it bears a greater share of its own security burden.

Second, South Korea must confront the possibility that a Taiwan contingency could intersect with a crisis on the Korean Peninsula through the dynamics of Sino-Japanese conflict. Japan’s expanding security role is closely linked to Washington’s effort to redistribute alliance responsibilities. Similar debates are already underway within the ROK–U.S. alliance, particularly regarding force modernization and the strategic flexibility of U.S. Forces Korea under the second Trump administration. USFK can no longer be assumed to exist solely for deterrence against North Korea; it may also function as a rapidly deployable asset in a Taiwan Strait scenario. This reality demands a reassessment of South Korea’s long-term defense planning.

Third, Japan’s increasingly rigid anti-China sentiment may complicate Korea–Japan relations and intensify regional instability. As political space for moderation in Japan continues to shrink, East Asia risks entering a cycle of escalating tensions. Such conditions could incentivize North Korea to tighten its alignment with China or Russia, further complicating the peninsula’s strategic environment.

For South Korea, cooperation with Japan is no longer a matter of political preference but of strategic necessity. Seoul must pursue a calibrated posture—managing relations with China, stabilizing ties with Japan, and preserving practical channels for trilateral coordination.

Ultimately, the Sino-Japanese confrontation is not a peripheral dispute. It is a revealing indicator of where the regional and global order is headed. Its evolution will shape the security landscape surrounding the Korean Peninsula in profound ways. Treating it as someone else’s problem would be a costly mistake.