The film centers on teenage girls navigating wartime duties and loss in Okinawa, with no transgender characters or themes present in its narrative.

The movie does not contain any action or adventure elements.

Cocoon: One Summer of Girlhood depicts the Himeyuri student nurses as an all-female group drawn from two all-girls schools, matching their documented historical roles and the source manga without any recastings that alter established genders.

The film adapts a manga about Japanese schoolgirls serving as nurses in Okinawa during World War II. All named characters originate from Japanese source material and are portrayed by Japanese actors in a period-accurate Japanese setting, with no recasting across racial categories.

Not depicted.