Memory of a Wildbird - S1.E16

The group takes a cruise boat to the continent where Edel Garden lies. Coud collapses after he is poisoned by a dart. During the night, Coud suddenly awakes and tries to kill Ren. Meanwhile, a Sting Raid poses people on board and drains their energy. Cisqua discovers her friend Myna, also a member Arc Aile, is the one who poisoned Coud and the Sting Raid. Myna is able to control their actions through a song that she and Cisqua both know. To save Ren from Myna, Cisqua is forced to shoot her. At the end of the episode, Cisqua begins to sing the song.