Rio Meilong serves as a bridge operator on the Hagane, driven by an unwavering passion for piloting Personal Troopers. Her ambitions clash with the concerns of her father, Yuan Meilong, director of Mao Industries, who disapproves of her combat aspirations despite her relentless simulator training. Cheerful yet fiercely competitive, Rio champions justice but bristles at criticism, often doubling down on her own perspective.

Ingram Plissken recruits her to the Hagane for her latent Psychodriver abilities, leading her to transition from support duties to active combat after demonstrating her prowess. Her rivalry with Ryoto Hikawa, a former Divine Crusaders pilot, begins with friction but matures into mutual respect, complicated by her unspoken romantic feelings. These emotions surface in flushed cheeks or sharp retorts when teased, adding tension to their dynamic.

During the Inspectors’ assault on Mao Industries’ lunar base, Rio flees with Ryoto and allies, commandeering the AM Gunner. Her unit later merges with Ryoto’s Huckebein MK III, forming the formidable Huckebein MK III Gunner—a testament to her combat adaptability. She juggles bridge operations and frontline engagements in battles against the Inspectors, Shadow Mirror, and Einst, proving her versatility.

A mistaken encounter with Kusuha Mizuha, whom Rio initially misidentifies as a civilian, blossoms into a steadfast friendship, underscoring her approachable demeanor. Undeterred by her father’s objections, she strives to validate her skills as a pilot, navigating both familial resistance and institutional barriers. Her trajectory—from operational support to battlefield leadership—showcases her tenacity and dedication to safeguarding others, cementing her evolution into a pivotal combat asset.