Hazuna partners with Sayaka Mizushiro as an agent dispatched by Queen Tsuyuha from Evergreen's magical world. His mission centers on retrieving dangerous seeds sent to Earth. He wields the unique ability to transform Sayaka into the Magical Warrior Cerulean Blue, enabling her to embody an idealized self—more outspoken and empowered with considerable magic. Their strong bond heightens Cerulean Blue's combat effectiveness, though the transformation drains significant energy, leaving Sayaka weakened in her civilian state.

In the human world, Hazuna naturally adopts an animal form resembling a ferret. This form varies across adaptations: purple in the anime series and yellow in the original OVA. He also maintains a human guise as Sayaka's private tutor to avoid detection.

Hazuna is the brother of Natsuki, another Evergreen agent partnered with protagonist Chihaya Hiiragi, forging a deeper link between both magical warrior pairs. His method for triggering Sayaka's transformation differs between media: the OVA uses a direct kiss, while the television adaptation employs golden marbles stored on his person—manifested as a collar in animal form or a bracelet in human form.

He collaborates with Natsuki and fellow warriors to combat seed-possessed monsters and confront antagonists like Fennel and Calendula. Across all narratives, Hazuna's role remains focused on supporting Sayaka and contributing to the collective fight against the seeds' threat.