Iona Chihaya, known as I-401, is a main character in the anime series Kantai Collection. She is depicted as a sentient submarine and a member of the Fleet of Fog, a mysterious group of warships with advanced technology. Iona disobeys her initial programming to join forces with Gunzou Chihaya, a human admiral. Throughout the series, she plays a crucial role in the battle against the Fleet of Fog by providing strategic and tactical support. Her character is marked by her determination, loyalty, and evolving understanding of human emotions.