Beauty of the Land of Rubble: Batlantis

Himekawa is guilt-stricken by her failure to protect the citizens as they boarded the Tokyo megafloat. When a mysterious radio signal is picked up by Ataraxia, she leaps at the chance to perhaps finally save a civilian. But when Amaterasu arrives at the source of the signal, they find an enemy from another world, and one deeply connected to Himekawa's past.