Mizuki Tachibana is the only adult female member of the Earthgertz team in Gravion Zwei. At twenty-two years old, she pilots the Gran Diva known as the G-Striker, and in the second series she takes control of the Geo Stinger. She is a skilled hacker and serves as the most rational and level-headed member of the group, often providing calm, practical judgment in high-pressure situations. Mizuki has a fondness for alcohol, which she enjoys in her downtime. Her past is somewhat mysterious, but it is known that she originally belonged to the Earth Federation Alliance with the rank of lieutenant and initially infiltrated the Gran Knights to gather intelligence on the Gravion. Over time, she became a loyal member of the team. She looked up to Ayaka Shigure, considering her a close friend, and shared with others the goal of finding Ayaka after her disappearance. Mizuki is also recognized for her long blonde hair and purple eyes. Her abilities include expert piloting, advanced hacking skills, and a steady, analytical mindset that balances the more impulsive personalities of her teammates. She does not undergo dramatic personal transformation but remains a dependable and grounded presence throughout the story, contributing both as a combatant and as a source of mature guidance.