Chloe is a mysterious figure that appears about halfway through the series, she claims to be the True Noir (her name may be significant, given the similarity in pronunciation between "Chloe" and "Kuroi", the Japanese word for black.) Though she is about Kirika's age, she is extremely skilled as an assassin, a quite remarkable fact since she uses throwing knives instead of using guns. Chloe is very faithful to Altena and works for the Soldats, enjoying a position of considerable authority.
She was witness to the murder of the Bouquet family by Kirika, an event which caused her to look up to Kirika. There are also strong suggestions later in the series that Chloe's feelings for Kirika are actually romantic.