Noir is a Magus, a type of android equipped with human-like emotions and designed to serve as the artificial intelligence partner for a Drifter piloting a Cradle Coffin mecha. She is the title character and the main female protagonist of the story. She is discovered by the aspiring Drifter Kanata while he is scavenging through the ruins of an old civilization building, where she had been slumbering in a state of long-term stasis. Upon awakening, Noir has no memory of her past or her origins, making her an amnesiac from the very beginning of the narrative.

Her personality is defined by a striking contrast between her everyday clumsiness and her extraordinary combat ability. In normal daily life, Noir is portrayed as something of a clunker, frequently struggling with simple tasks such as putting on clothes properly or helping around the house. This endearing helplessness gives her a somewhat vulnerable and childlike demeanor, which can evoke a desire in others to look after her. Despite these domestic shortcomings, she possesses an unmatched prowess in battle. Within the cockpit of a Cradle Coffin, her capabilities as a Magus are remarkably high, allowing her to perform effectively and with great skill against the hostile creatures known as Enders. This dichotomy between her uncoordinated civilian behavior and her sharp, powerful combat instincts is a central trait.

Noir's primary motivation throughout the story is to recover her lost memories and discover the truth about who she is and where she came from. This personal quest drives her forward and intertwines with the larger goal of locating the mythical city known as Histoire, a place that holds secrets about the world that Kanata dreams of visiting. Her journey is not simply about regaining the past but also about forging a new identity and purpose in the present.

In the story, Noir serves as Kanata's Magus partner, registered as the AI for his Cradle Coffin unit, the Daisy Ogre. Her role is essential to his development as a Drifter, as her combat excellence enables him to face the dangers of the surface world effectively. She is the catalyst for the central adventure, as her discovery sets both her own quest for answers and Kanata's dream of reaching Histoire into motion. She forms a close bond with Kanata, built on mutual trust and reliance during their missions. She also becomes part of a small squad that includes Kanata's friends Tokio and Ellie, integrating into their group as they support one another.

Her key relationships include her partnership with Kanata, which is the emotional and functional core of the story. Through him, she experiences the world and slowly begins to build new memories. The dynamic she shares with other Magus characters and Drifters further explores the nature of her abilities and her mysterious past. A significant aspect of her character development involves the revelation that another Magus named Mystere, through a hack of the Histoire network, received Noir's appearance and personality, meaning that Noir and Mystere effectively share the same body. This revelation adds layers of complexity to her identity and forces her to confront the question of what truly defines a person.

Over the course of the series, Noir evolves from a lost and memory-less entity into a more self-aware individual. Her journey is one of self-discovery, where she learns not only about her forgotten history but also about her own value and place in the world. The narrative challenges her to define herself beyond her past and to embrace the bonds she forms in her present life.

Her most notable ability is her exceptional talent in operating a Cradle Coffin during combat. Despite her amnesia, she retains a high degree of skill and effectiveness in battle, making her a formidable asset against the Enders. This natural combat capability stands in stark contrast to her clumsy behavior outside of combat, marking her as a uniquely gifted Magus whose abilities are deeply ingrained even without conscious memory of them.