Kai Nakamura, childhood friend of Kukuru Misakino and older brother of Maho Nakamura, comes from a family deeply rooted in the fishing trade. Each dawn, he aids his father in hauling catches to supply Kukuru’s family, sustaining their shared livelihood. When summer arrives, he dedicates his breaks to volunteering at the endangered Gama Gama Aquarium, driven by loyalty to help Kukuru stave off its closure. After the aquarium’s eventual shutdown, he shifts seamlessly to Tingarla Aquarium, joining Kukuru in the Aquatic Animals Department to continue nurturing marine life.

Quiet and composed, Kai masks his supportive instincts behind a practical, efficiency-focused exterior. His disciplined nature—marked by diligence, reliability, and a methodical adherence to tradition—shapes his approach to both work and family. Juggling aquarium duties with filial responsibilities, he quietly safeguards those around him, balancing protective vigilance with understated care. Beneath his reserved demeanor simmers a fervent passion for marine ecosystems, propelling him to refine his aquaculture expertise relentlessly.

As a steadfast anchor in Kukuru’s endeavors, Kai’s lingering glances hint at unvoiced affection. His bonds extend beyond her, evident when he guides sister Maho and childhood companion Tsukimi Teruya through Tingarla’s exhibits, reinforcing his enduring ties to the community. Through unwavering commitment to growth—both personal and professional—he earns respect as an indispensable pillar of the aquariums he serves, ensuring their legacy thrives.