Aika Sumeragi is a highly skilled professional salvager who recovers valuable artifacts from the depths of the ocean in a world where much of the Earth has been submerged following a catastrophic earthquake. Orphaned as a child when her scientist parents perished in the same disaster, she was raised by a man named Gozo Aida, who trained her in salvaging, combat, and firearms. She earned her C-class license at sixteen and would eventually become one of the best in her field. Aika is defined by strong professional dedication and a pragmatic, adaptable approach to high-risk missions. Despite being the center of frequent fan service, she is personally uncomfortable with overt sexuality and becomes flustered in such situations. A key element of her character is a golden bustier made of a material called ultranate, which can transform her into a superpowered state known as Shivie Aika. In this form, her skin darkens, her hair turns blue, and she gains immense strength, resilience, limited regeneration, and the ability to manipulate the metal for attacks or defense. She dislikes relying on this transformation and tries to avoid it, though it often activates automatically in life-threatening emergencies. Even without the bustier, she is formidable in hand-to-hand combat, skilled with firearms such as tranquilizer dart pistols, and an accomplished pilot of aircraft and other vehicles. Over the course of her career, she works closely with Gozo’s daughter, Rion Aida, and frequently clashes with rival salvager Gust and the all-female Delmo Corporation. Her development spans from an inexperienced teenager still in training to a confident and capable adult, though she consistently struggles with her feelings about her artificial enhancements.