Yuki Hanazomon is a pink-haired high school student living in Sorasaki, usually seen in her school uniform outside missions. Clumsy yet fiercely driven by a strong sense of justice, she deeply idolizes Momo Minamoto as her ideal. Her desire to protect others fuels her aspiration for strength, leading her to uncover Momo's secret role within Tsukikage, a covert organization protecting the city. After witnessing Momo in action, Yuki is personally recruited by her into Tsukikage as a novice agent.

Under Momo's guidance, Yuki trains rigorously, learning espionage, combat skills, and utilizing the organization's signature spice-based enhancement substance. Her training emphasizes agility and stealth mastery. She forms strong bonds with fellow novice agents Hatsume Fujiwara and Fuu Sagami, integrating into their team.

Yuki's motivation is rooted in personal history: her father, a Tsukikage agent, was killed by the leader of the opposing organization, Moryo. This tragedy fuels her resolve to fight Moryo and protect Sorasaki from their criminal threats. On missions confronting these threats, Yuki evolves from an inexperienced recruit into a capable agent, her determination and sense of justice remaining central.

The conflict intensifies when Moryo captures Momo. Yuki joins the high-stakes rescue operation, culminating in a direct confrontation with the Moryo leader responsible for her father's death. This pivotal moment tests her resolve and skills. Following the major conflict's resolution, Yuki continues her dual life as a high school student and active Tsukikage agent, committed to protecting Sorasaki alongside her teammates. Her journey reflects a progression from admiration to active participation and personal resolution within the covert world.