Kyodo says Japan has decided to accelerate the study of deploying the Aegis Ashore missile defense system in the country.
By Commander, U.S. Naval Forces Europe-Africa/U.S. 6th Fleet (Aegis Ashore Missile Defense Complex Romania) [Public domain], via Wikimedia Commons
The Aegis system is preferred over the Terminal High Altitude Area Defense (THAAD) has the former is cheaper to deploy. Only two Aegis sites are required to cover the entire country.