One of the most important defining features of Japan's "Free and Open Indo-Pacific" (FOIP) vision is coalition-building. Given the Yoon administration's strong political will to commit to the Indo-Pacific affairs and improve its ties with Japan, can Japan and South Korea finally forge cooperation in the Indo-Pacific region? I argue that Japan has not incorporated South Korea in its FOIP vision because of four main factors: timing, leadership transition, commitment to regional and global strategic affairs, and differing perspectives on China. Particularly, the negative impact of South Korea's leadership change and its fluctuating commitment to regional and global affairs have nurtured Japan's skepticism toward South Korea's potential role in the Indo-Pacific region. In this context, the key to overcoming such difficulties and incorporating South Korea into the Indo-Pacific network depends on the Yoon administration's conceptualization and institutionalization of its Indo-Pacific strategy and Japan's support for South Korea's current diplomatic activism