The sister of Naomasa, Musashi Ariadust Academy Sixth Special Agent. Her name is unknown and she's residing inside the God of War Jizurisuzaku as a living organic Operative System, replacing the original Suzaku OS.
One day, their hometown was attacked, and Jizurisuzaku didn’t move due to a malfunction in the OS. They would end up being completely wiped out, but at that moment, Naomasa’s sister, mortally wounded, asked Naomasa to use her, becoming the new foundation to the God of War. Since that day, Naomasa little sister lives inside the God of War in an ether powered blue cylinder, missing most of her original body.
In the original novel, her shape was seen through a Toori shaped Sign Frame Divine Correspondence, but in the animation she was shown in her ether chamber. Also, in the novel she was described as a young girl when in the anime she looked like a busty girl more or less the same age as Naomasa. This can be explained as she's indeed growing normally inside the God of War, but the incident with their village was not that many years ago, so it still remains a mystery.