Hina Mitsurugi, a 16-year-old high school freshman in Neo Hong Kong, balances typical teenage routines with an intense passion for wrestling and arcade gaming—interests deemed unconventional for her gender. These pursuits often dominate her focus, causing neglect of other duties. She lives independently; her mother remains absent for undisclosed reasons, and her father travels frequently for work. Though self-reliant in household management, her maturity lags behind these responsibilities.

Her personality blends impulsiveness, liveliness, and simplicity. She reacts to criticism with a quick temper and shallow defensive retorts, particularly evident in clashes with Cindy Shahani. Hina habitually mocks Cindy’s breast size, exposing her own insecurities about her physique—attempts that routinely backfire. Her interactions with Reika Fou prove less contentious.

A catastrophic roof collapse at a wrestling match with friends Natsuki and Megumi transports Hina to an unknown realm. There, she learns she is a destined "Kaiser," piloting the ancient mecha Dangaizer 3—a colossal weapon from 8,000 BC that once judged humanity. Hina commands its primary Standard form for close combat, joining Cindy (Kaiser Dragon) and Reika (Kaiser Neptune). Adaptation is fraught: memory loss clouds her understanding of her role amid escalating conflict. When Goma, an organization seeking Dangaizer 3’s destruction, attacks Neo Hong Kong using elemental Guardian Deities, Hina must leverage her gaming skills in real combat against foes like fire-based Gaiflame and wind-based Gaistorm.

Goma’s warriors target her relentlessly. She first battles Sapphire in Gaiflame, then confronts Eileen—a Goma-engineered double resembling Hina physically but radiating unexplained hostility. Later, she faces Deene piloting Gaistorm. The conflict concludes ambiguously: the series’ cancellation after four episodes leaves Hina’s fate unresolved, halting exploration of her growth, the Great Dangaizer, Bloody Dangaizer, and the dormant earth-based Gaiearth.