Luna Mochida plays sea diver Rio Mochida, who fights as the heroic warrior Sailor Tetis against the demon Skullton. To strengthen her abilities, she begins training under her father, professional wrestler Kenzo Mochida. However, as her training progresses, Skullton discovers Kenzo's connection to her and deceives him, leading to his abduction. Upon learning of her father's capture, Rio resolves to fight and save him. But waiting for her is the monstrous golem. Transforming into Sailor Tetis, Rio engages in a fierce battle with the golem, eventually being cornered and overwhelmed. At a critical moment, she notices the golem bears a striking resemblance to her father. Soon after, she encounters Kenzo, restored to his former self. Yet, Kenzo tells Rio to defeat him, leaving her torn. Though she hesitates, still believing in her father's true nature, she resolves to fight—only to falter at the last second and suffer defeat. Captured by Skullton, Rio loses her sense of justice, succumbs to darkness, and swears allegiance to Skullton as a demon warrior.