Discover Call

A Discover Call (存在共鳴(ディスカバーコール), Disukabā Kōru, Existence Resonance) is a unique type of noise emitted by Unions whenever they use their Drive. While usually dependent on the Union who is producing the sound, the noise typically extends to around 10 meters (32 feet).

Tōya Kagari, for some unknown reason, possesses the unique ability to hear Discover Calls from a distance of 300 meters (984 feet), Es can also hear the calls due to a special system installed on her. After Es inherited the Embryo from Hinata Himezuru, she could hear a special type of Discover Call that helped her locate the Master Unit within the Boundary.