Juno Cassidy operates as a CIA agent under the cover of an NYU professor, gathering intelligence from archaeologist Koichiro Kamishiro about ancient artifacts. Posing as an archaeologist, she collaborates with him during an Israeli desert expedition. After guerrillas attack their team, they discover a mysterious cube-shaped stone inscribed in an ancient language. During their escape, hostile forces hijack their plane; Cassidy eliminates them while Kamishiro rests, demonstrating combat expertise with firearms including an unnamed pistol.

Surviving the plane crash, she resurfaces during the investigation of the sacred mirror Yatanokagami at Himiko's shrine. Her CIA allegiance emerges when she confronts Kamishiro's group and opposes Grigori Yefimovich, a KGB agent codenamed Urga. She engages Urga in armed combat using automatic weapons and rockets, prioritizing the mirror's retrieval for CIA objectives amid the geopolitical conflict over the "Message of God."

Her motivations center on executing CIA directives regarding ancient artifacts, specifically the Crystal Triangle and Yatanokagami. Multilingual, she communicates in English among CIA associates while maintaining her cover. Her interactions with Urga feature professional rivalry and tactical opposition during shrine confrontations.