Kasane Agura is a scientist working for the organization IX in the anime series M3 the Dark Metal. She is a woman with dark brown hair and dark brown eyes, typically seen wearing a purple top, a black skirt, stockings, and a lab coat. Her personal life is deeply intertwined with her professional role, as she was the girlfriend of Aoshi Saginuma, the older brother of the pilot Akashi Saginuma. Following Aoshi's death in the Lightness Realm, Kasane becomes Akashi's guardian, a role she requested, though she eventually comes to regret placing him on the team of MA-Vess pilots. She also maintains the apartment where she, Aoshi, and Akashi once lived together, even though she no longer resides there.

Kasane possesses a caring and sympathetic personality, particularly toward the MA-Vess pilots and their difficult circumstances. This compassionate nature often puts her at odds with her superior, Natsuiri, who views the young pilots merely as tools for combating the threat of the Lightness Realm. Her protective instincts are especially directed at Akashi, feeling a strong sense of responsibility for him after his brother's demise. However, her motivations are complicated by her grief over Aoshi; she seems to unconsciously try to use Akashi as a replacement for his deceased brother, a behavior that Akashi recognizes and resents, leading him to treat her coldly at times. This dynamic is a key part of her internal conflict and her relationships within the story.

Kasane’s role in the narrative is primarily that of a supportive adult figure within the harsh environment of the research academy. She represents a voice of moral hesitation and empathy, clashing with the more pragmatic and ruthless methods of her colleagues. Her opposition to Natsuiri's cold approach to handling the pilots demonstrates her resistance to the idea that the children should bear such a brutal fate. In moments of vulnerability, such as when drinking at a bar, she has openly expressed her anguish over the harsh destiny forced upon Akashi and the other young pilots.

Throughout the series, Kasane experiences significant development as she navigates her grief and her changing relationship with Akashi. Her initial desire to protect him is gradually overshadowed by the painful awareness that her actions, specifically requesting his placement on the team, have contributed to his suffering. This leads to a strained and complex bond where her attempts at care are often met with his anger and distrust, forcing her to confront her own misguided attempts to fill the void left by Aoshi. Her notable abilities lie in her scientific expertise, which she applies to her research and the support of the MA-Vess project, though her primary impact comes from her emotional and relational struggles within the story.