Kozumi is a dedicated fan of Amane Todoroki, consistently enjoying and believing in her magic performances despite any onstage mistakes. She supports Amane as part of Nought group's small audience, initially unaware Amane's abilities derive from supernatural Incomprehensible Skills of Human beings (ISH), perceiving them as remarkable magic tricks.

Her involvement intensifies when rival group IAM targets her during experiments on ISH users. Kidnapped by a man whose artificially awakened ISH powers spiral out of control, Kozumi triggers a crisis forcing Amane and her twin sister Lilianne to fully fuse. This fusion unleashes Lilianne's immense power, enabling Amane to rescue Kozumi. During the rescue, Kozumi witnesses Lilianne's true spirit form and learns the supernatural truth behind their abilities. Rather than fear or rejection, she responds with heightened admiration, cementing her loyalty to Amane.

Subsequently, Kozumi remains a visible supporter within Amane's fanbase, frequently appearing alongside fellow fan Mana. She continues her unwavering attendance at Nought group performances.