Marina, also known as Umi Ryuuzaki, is one of the three main protagonists of the Magic Knight Rayearth story. She is a fourteen-year-old eighth-grade student from a wealthy family in Tokyo and the only child of doting parents. Marina is tall and strikingly beautiful, with long, flowing silver-blue hair and dark blue eyes. She is a skilled fencer and serves as the captain of her school’s fencing team, a talent that directly translates into her combat style in the magical world of Cephiro.

Initially, Marina comes across as spoiled, quick-tempered, and reluctant to accept her situation. When she, along with Hikaru and Fuu, is summoned to Cephiro, she is the most resistant and skeptical of the three. She complains about the absurdity of the adventure and longs to return to her comfortable life, especially because she is under pressure to attend an important fencing contest. However, beneath her proud exterior lies a fiercely loyal and protective nature. As the story progresses, she sheds much of her selfishness and becomes the self-appointed big sister of the group, looking after Hikaru and Fuu with genuine care. Her strong will and determination make her a formidable ally, and she is often the one who provides comic relief through her exaggerated reactions, especially in her ongoing rivalry with the creature Mokona, whose playful behavior constantly irritates her.

Marina’s motivations evolve over time. Driven at first by the desire to return home, she gradually grows to care deeply for Hikaru and Fuu and for the fate of Cephiro itself. In the second arc, she returns to Cephiro voluntarily, no longer out of obligation but out of a genuine wish to help the world she has come to love. This marks a significant maturation; she becomes more controlled in battle, more empathetic, and more willing to put others before herself.

As the Magic Knight representing the water element, Marina wields a rapier forged from the mineral Escudo, which melts into water if touched by anyone other than herself. Her magical abilities include water-based spells such as Water Dragon, which summons a massive dragon-shaped stream of water, Blue Tornado (also called Azure Hurricane), a high-pressure waterspout, and later Ice Blade, one of the strongest ice spells. She also participates with Hikaru and Fuu in the combined attack Spiral Flash, a vortex of light that combines all three elements. Her Rune-God, or Mashin, is Selece, a blue bat-winged sea dragon that takes the form of a giant robot when she pilots it.

In terms of relationships, Marina forms a close, sister-like bond with Hikaru and Fuu. She and Fuu often take on protective roles toward the more impulsive Hikaru. Her interactions with Mokona are famously combative, but she eventually develops a grudging affection for the creature. In the anime, she has a crush on the sorcerer Clef, who remains indifferent to her feelings, while the boy Ascot secretly admires her without her noticing. The manga portrays a different dynamic: Marina has a closer, more proactive connection with Ascot, and her feelings toward Clef are more respectful than romantic. She also becomes friendly with the twin princesses Tatra and Tarta of Chizeta, whom she defeats in sword fights.

Marina’s role in the story is essential. She is one of the three chosen Magic Knights summoned to save Cephiro by defeating the high priest Zagato and rescuing Princess Emeraude. When the truth emerges that the knights were actually meant to kill the Pillar, Marina must confront the emotional weight of that mission. In the second arc, she helps defend the remnants of Cephiro from invading planets and supports Hikaru’s decision to abolish the Pillar system entirely. Throughout the journey, she grows from a self-centered girl into a mature, compassionate, and courageous young woman. Her fencing prowess, water magic, and unyielding loyalty make her an indispensable part of the team.