Capability and domestic credibility are two essential components of national security, though little has been examined as to the latter. Domestic credibility is a feeling of safety by the public, which is created or damaged by policy process in relation to national government.Japan's national security policy from the 2000s showed a confrontational posture in relation to China, but its policy of domestic credibility has not been well managed in terms stabilizing relations with China. Postwar Japan adopted a pacifist national security policy in which capability and domestic credibility were harmonized under the 1947 pacifist constitution.Japan had a special relationship with China which was respected under the policy of "China particularism". Japanese leaders adopted a concessional attitude towards China, making concessions to facilitate friendship diplomacy in the 1970s-80s. In the face of a rising China, this postwar China policy gradually changed and was discredited from the 2000s. Japan's defence policy came to define China as its object. Pacifist constraints on defence planning and military deployments were weakened and "territorial defence" of the south-west island chain became the leading concept in the 2010s. Japanese neo-conservative political elites adopted non-concessional attitudes over history and the Senkaku/Diaoyu islands, and allowed political and security issues to escalate with China. In the U.S-Japan alliance, Japan began to insist on deterrence against China, which was a completely different posture compared to the 1990s when Japan attempted to mitigate the impact of the alliance on China. In view of these changes in capability and external postures, domestic credibility was gradually transformed, but was not stable. Japan increased its defence capability against China, but it only resulted in China's counter-measures. Japanese neo-conservative non-concessional attitudes resulted in a deterioration of relations with China. Japan's resort to deterrence through the US alliance was iv not endorsed by the United States, it was basically domestic language for the Japanese public who believed that the alliance was almighty for Japan's national security. Japan's emerging national security was distorted by the inclusion of national pride and did not allow for the stabilization of relations with China. This confrontational policy employed a one-sided public justification and resulted in a polarization of opinion in the Japanese public. National security requires domestic credibility, and without it there may be tensions. How to manage domestic credibility by public justification is the key to the achievement of national security.