Najica Hiiragi is a renowned perfumer at CRI Cosmetics, celebrated for identifying over 500 distinct scents. She develops "The Day Series," perfumes inspired by days of the week, with "Sunday" posing a persistent challenge.

Secretly, she serves as a covert field agent in CRI's clandestine Intelligence Bureau, unknown to the public and most employees. Missions activate upon receiving a single rose, focusing on recovering rogue Humaritts—humanoid androids—from criminals, revolutionaries, or terrorists. She pilots a custom Mil Mi-35 Hind assault helicopter and employs a Stechkin APS pistol loaded exclusively with non-lethal plastic bullets.

A critical mission involves retrieving the Humaritt "ZZZ" (later named Lila) from a bisexual countess intending to use her as a sex toy. Despite Najica's preference for solo operations, her superiors assign Lila as her partner. Initial friction arises from Lila's lack of social understanding and emotional expressiveness, compounded by Najica's suspicions about CRI's contracts with Shinba Industrial to recover more Humaritts.

Through successive missions, Najica evolves from resenting Lila's presence to embracing mentorship, teaching societal norms and protocols while occasionally questioning her own methods. Their partnership deepens against escalating threats, including Humaritt creator Dr. Ren (Triple X), whose schemes test their alliance. Najica grows fiercely protective of Lila's autonomy and safety.

Her development culminates in granting Lila independence: Najica allows her to depart with another Humaritt, Alpha, affirming Lila's personhood through this act of trust.