Fuyajou no Assassin  

Assassin of the Nightless City, Wu Zetian, 不夜城のアサシン

In order to rescue her father who had been abducted, a young girl disguised as one of the Chaldeans infiltrated Dahut's palace. While Dahut was occupied with fighting battles, the young girl managed to steal the key that would unlock the floodgates of the city. After accomplishing her mission, Assassin boasted about his success to both parties before leaving. Unfortunately, Ys, as depicted in legend, sank beneath the waves, leaving very little for the Resistance to salvage or rescue.