Kamome Kushima is a 17-year-old girl spending summer on Torishirojima Island, coinciding with Hairi Takahara's visit. Her surname combines "long time" and "island," while her given name means "seagull," reflecting her seaside connection. Standing 158 cm tall and weighing 43 kg, she has indigo hair typically in twin tails with spiky bangs and striking amber eyes. A distinctive skull-and-bones hairpin adorns her hair, hinting at adventure. Her practical exploration attire includes thigh-high stockings, lace-up shoes, and sundresses, though she occasionally wears a maid's dress or school uniform. Kamome blends curiosity, whimsy, and bluntness. She possesses an airheaded, carefree demeanor, often meddling in situations purely out of curiosity, sometimes leading to danger. Despite her refined background, she exhibits mischievous and hot-blooded tendencies, teasing others and embarking on spontaneous adventures. An air of mystery surrounds her, especially concerning the large suitcase she constantly drags behind her, whose contents she keeps secret. She uses this suitcase cleverly during explorations and even rides atop it when tired. Her lighthearted, casual speech treats strangers like old friends, evoking nostalgia. Hailing from a wealthy family, Kamome shares a close bond with her mother, Sagi Kushima. She journeys to Torishirojima driven by an old map she believes is a treasure map leading to a fabled pirate ship, inspired by childhood stories told by Hairi's grandmother, Katō. Katō originally gave them the map, symbolizing a promise of shared exploration. Kamome's motivation stems from her mother's deteriorating dementia; Sagi confuses past and present, reenacting Katō's treasure hunts believing Kamome is still a child. Kamome aims to recreate these hunts to preserve her mother's cherished memories. During her route, Kamome partners with Hairi to explore a cave at low tide. They discover a weathered suitcase containing a book documenting Katō's adventures with a young Sagi, revealing the map's origin and contextualizing Kamome's quest. This coincides with the appearance of Shichieichō butterflies—supernatural entities embodying lingering memories—which guide Kamome and Hairi back to Sagi. The reunion allows Kamome to share her findings, briefly reconnecting her mother to reality. Though Sagi's dementia persists, Kamome achieves closure by fulfilling their shared dream. Her character shifts from a secretive adventurer to someone confronting familial love and loss, emphasizing memory preservation. She departs the island at summer's end. Kamome is a daughter dedicated to easing her mother's illness. Her dynamic with Hairi blends camaraderie and nostalgic familiarity. She interacts with other island residents through group activities like table tennis and youth association events. Her hobbies include creating intricate ships in bottles and savoring triangular-shaped sweets with hidden fillings, reflecting her fascination with seafaring lore and playful secrecy.