Kukuru Misakino, an 18-year-old high school student on summer break, serves as acting director of Okinawa's financially struggling Gama Gama Aquarium. She possesses an exceptionally strong attachment to the aging facility, dedicating herself to preventing its closure despite deteriorating infrastructure like peeling paint, rusty metalwork, and malfunctioning equipment. Her tireless efforts focus on generating necessary funds through creative initiatives and hard work to cover operating costs and maintenance.

This deep connection stems from personal tragedy: losing her parents young, she was raised by her grandfather, the aquarium's official director. Consequently, she views Gama Gama not just as a workplace, but as the embodiment of her dreams and a source of emotional stability. Exhibiting a straightforward, upbeat, and passionate personality, she speaks harshly when the aquarium's interests are challenged. While possessing extensive expertise in marine life, she lacks familiarity with current fashion trends and initially demonstrates limited people skills.

Kukuru experiences supernatural phenomena at Gama Gama, including visions of aquatic spirits and a local Okinawan kijimuna, which initially guide or reflect her emotional states. These occurrences diminish as she matures and shifts focus toward practical responsibilities. Following Gama Gama’s inevitable closure, she graduates high school and secures a position at the newer, larger Tingarla Aquarium through her grandfather’s recommendation. Contrary to her expectations of working directly with marine animals, she is assigned to marketing and public relations under strict Vice Director Tetsuji Suwa, who nicknames her "Plankton."

This career shift forces Kukuru to confront new challenges. She struggles with the disconnect between her idealized vision of aquarium work and the realities of corporate responsibilities, feeling initially demoralized by administrative tasks and customer interactions. Over time, through perseverance and support from colleagues like close friend Fuuka Miyazawa (a former idol she met at Gama Gama), she gradually adapts. She develops competence in event planning, public engagement, and teamwork, learning to channel her passion into creating memorable visitor experiences, such as organizing a successful aquarium wedding. Her interpersonal skills improve significantly, earning respect from initially critical superiors.

Kukuru’s development culminates in a renewed sense of purpose. She reconciles her love for marine life with her marketing role, recognizing that protecting aquatic environments requires both direct care and effective public outreach. In a pivotal moment, she experiences a vision of her deceased parents and unborn sister expressing pride in her growth. By the series’ conclusion, dedicated to Tingarla, she has evolved from a single-minded idealist into a resilient professional capable of navigating setbacks while staying true to her core values. Two years later, she continues advancing in her career, symbolizing a journey from naive determination to mature adaptability.