Natsumi Kanno is the central protagonist of the STAR Jewel media. Her youth included attendance at Santa Maria Academy, where puberty revealed her unique physiological trait: a retractable penis. This period involved interactions with the student council president, who later exposed darker intentions.

A significant arc saw Doctor Genetick send her to a dystopian past version of Budapest. There, antagonist Armande Ten brainwashed her into believing she was a regular student. Mechanic Juni Soremov exposed Armande's scheme of abducting girls responding to event invitations, restoring Natsumi's memories and mission. This led Natsumi to confront Armande, stop the operations, and return to her original timeline.

In the primary timeline, Natsumi operates as a goddess of light in Budapest, combating the dark goddesses led by General Rhino (Zircon/Larra). These adversaries steal energy crystals—manifestations of life force—from innocent women, leaving them lifeless husks. As part of the "Drivers" or "Jewels" team, Natsumi and her allies retrieve these crystals to return them. Her role involves undercover operations, often disguised in professions like train drivers or mechanics to infiltrate and disrupt enemy activities.

Physiologically, she possesses a flower-like organ in her chest housing energy crystals, consistent with all goddesses in this universe. Her primary combat method utilizes her retractable penis to overwhelm opponents via sexual penetration, a shared tactic among both factions to incapacitate enemies through pleasure.

Codenamed "Diamond" during missions, Natsumi participates in interdimensional efforts to prevent dark forces from harvesting enough crystals to power a spacecraft. Success would enable their return to their home planet, an outcome the light goddesses strive to prevent.