Rusmira is a mermaid possessing a bright blue tail with glistening scales and long blonde hair. She plays a critical role in the narrative, known for her brave and determined nature. Confident and focused despite challenges and danger, she consistently works to protect her people and prevent destruction, distinguished by her strong will and courageous attitude.

Her relationships significantly shape her portrayal, particularly a special bond formed with the main character Masato. Their evolving interactions reveal aspects of her personality, highlighting themes of love, loyalty, and friendship while demonstrating meaningful cultural unity. Her role extends beyond individual relationships as she actively opposes forces threatening her world.

She exhibits traits of strategic thinking and introspection. She approaches problems logically and analytically, often planning and organizing solutions, aided by intuition and adaptability to navigate complex situations. Sensitivity and creativity also emerge in her characterization, reflecting an independent yet empathetic nature.