In June 2020, Japan’s Ministry of Defense (MOD) abruptly announced it would abandon the Aegis Ashore deployment plan. Then, after twists and turns in policy coordination between the government and ruling parties, the Cabinet decided on December 18 to build two Aegis system-equipped vessels to replace the Aegis Ashore system. How will the shift from deployment of two land-based Aegis systems to construction of two sea-based Aegis system-equipped vessels impact Japan’s “comprehensive air and missile defense”? What are Aegis system-equipped vessels, and what should be their operational concept? Akihisa Nagashima, Member of the House of Representatives of Japan, offers his thoughts on these issues.