Saki is an agent working with Kazuya Katagiri, Kei Yuki's former love. Masquerading as his niece, she attempts to pump Kei for information regarding the Arcadia's curious behavior at Aman's sea-floor base while Kei is attempting to help Kazuya carry on her father's work. The discovery that Saki is a Mazone leads Kei to the unavoidable conclusion that Kazuya has betrayed her and humankind.