Doumu Kai piloted Gaia Zenon as its main operator within the Zenon Guardians, commanding the Gaia Base that served as the core body of the machine. Before confronting the Zeno Palace alien forces, she sustained herself as a band vocalist through live performances after becoming orphaned in childhood. Her musical path concluded when the Matsunohara Family recruited her as Gaia Zenon’s inheritance pilot.

Despite her gender, her boyish appearance and speech patterns frequently caused others like Kana to misidentify her initially, a trait that persisted. She exhibited extreme sarcasm and a predominantly cool-headed disposition, though stress could trigger impulsive reactions. Her sharp, mocking remarks often targeted Akira Kamui’s hot-headedness. This culminated when Tri-Zenon used Gaia Zenon as a stepping stone via a spin-toss during a Kyushu battle; enraged, she retaliated by firing at him.

The final clash with Zeno Palace unveiled her genetic identity: she shared identical genomes with Cecil Grenade, younger sister of Zenon Empire general Duran Grenade. This revelation prompted her to stay with the Zenon forces post-battle. Heterochromia marked her eyes as distinctly different colors.