Kotori Misaki, a junior high student with dark blue hair and violet eyes, balances her role as Kokoro Misaki’s older sister and Kodama Kohinata’s classmate. Her surname, meaning "cape," subtly nods to coastal ties. Introduced as a supporting figure, she crosses paths with Futaba Ooki amid the Yamayaki Festival’s smoky chaos, where Futaba’s separation from her group sparks an unexpected team-up with Kotori and her brother, Kokoro. Despite their first meeting, Kotori senses an unexplained familiarity with Futaba.

Later, Kotori and Kodama join Futaba and Hikari Kohinata at their high school, entering the diving club. Together, they venture to meaningful sites like one discovered earlier by Kino Kohinata, weaving personal history into their underwater explorations. These shared dives mirror the series’ focus on forging bonds through new experiences.

Kotori’s arc centers on family ties and her steady immersion into the diving world. Her evolving dynamic with Kodama and peers charts a path toward teamwork-driven discovery, though her personal motivations remain unexplored. Through club activities, her relationships highlight growth and legacy within the ensemble, anchoring themes of continuity amid collective adventure.