By comparing the balancing strategies ‘Anti-Access’ and ‘Air-Sea Battle,’ this paper approaches the implications for the Korean Peninsula and East Asian security. China's active defense strategy proceeding to power transition in East Asia has been evaluated to cause the US's strong responses to mobilize military and diplomatic countermeasures, namely 'Pivot to Asia.' In this context, to maintain peace and the status quo, regional countries should participate in the appropriate control of the "Shared Regional Hegemony" which means neither accepting too much of China's assertion nor agreeing to excessive military strategies of the US. To reduce the impact of the two rival strategies, as a supporting or coordinating actor, the Republic of Korea (ROK) must properly utilize 'ROK-US-China' and 'ROK-US-Japan' triangles based on the ROK-US alliance, while she has to pursue unilateral initiatives and invite reciprocation of North Korea as a long-term strategy for cooperation. Finally, to prevent regional conflicts, regional states should establish a legally binding mechanism. The legally binding mechanism needs to pursue a middle course between the regional alliance and the multilateral security cooperation system to control the two giants’ (the US and China) unilateralism, as a kind of collective security system in East Asia.