Nagisa Misumi is an outstanding athlete and daring girl that doesn't take time to study but has a very strong sense of justice. Honoka Yukishiro is an honor-roll student always boasting the best grades in her class. The two are 8th graders at the Verone Junior High School for girls. Nagisa and Honoka each encounter Mepple and Mipple – two mysterious creatures who came down from the sky one night. These two strange creatures grant Nagisa and Honoka the power to transform into superheroes called "Cure Black" and Cure White", and thus the two girls become guardians of planet Earth.