Iona is the sentient mental model of the submarine I-401 and one of the main protagonists in the anime series 'Aoki Hagane no Arpeggio' (Arpeggio of Blue Steel). As an advanced AI vessel from the mysterious Fleet of Fog, Iona develops a close bond with her human captain, Gunzou Chihaya. Throughout the series, she demonstrates loyalty, curiosity about humanity, and a willingness to defy her original programming, playing a crucial role in the struggle between humans and the Fleet of Fog.