Full name: Manatsu Natsuumi. First person: I (energetic, polite). Second person: Name only or with -kun/-chan. A first-year middle school girl who is as bright as the midsummer sun and full of motivation for everything. She is in Class 1-5 at Aozora Middle School. Her catchphrase is "I'm feeling tropical!" She is the type to act before she thinks, always believing in "doing the most important thing right now!" She is a high-tension character who rushes forward with intense emotions. However, she possesses a strong core and stays true to her decisions, even if it means facing mysterious monsters empty-handed. She treasures a lipstick given to her by her mother. She believes that "makeup is a kind of magic" because putting it on fills her with courage and a sparkling feeling. While Manatsu is a bundle of energy who marches to the beat of her own drum, she isn't socially oblivious. She notices immediately if her jokes fall flat. She has chestnut hair and green eyes. Her hairstyle is a side-tail on the left side of her head, tied with a yellow ribbon. Her large front teeth, like those of a rodent such as a mouse or squirrel, are a prominent feature. She lives in her mother's room at the Aozora Aquarium staff dormitory. She transforms into Cure Summer using the Tropical Pact.

Full name: Sango Suzumura. First person: I (polite, feminine). Second person: With -kun/-chan. A first-year middle school student in the same class as Manatsu Natsuumi. A kind-hearted girl who is always smiling and cannot overlook people in trouble. She is good at being attentive and can get along with anyone quickly. In truth, she has a timid personality and lacks self-confidence, but because she is cautious and tries not to cause friction by blending in with those around her, she manages to hide her own weakness. She has dark blue hair and wisteria-yellow eyes. Her hairstyle consists of pigtails tied with pink or light red ribbons, with a single cowlick. This cowlick stands up straight or turns into a heart shape depending on her emotions and senses. She wears red hairpins shaped like "-" and "x" on the right side of her head and triangular yellow and light green hairpins on the left. Her family runs a cosmetic shop called "Pretty Holic." She transforms into Cure Coral using the Tropical Pact.

Full name: Minori Ichinose. First person: I (polite). Second person: By name. A second-year girl (Class 2-2) at Aozora Middle School. She is Manatsu and Sango's senior and Asuka's junior. Before transforming, she is a quiet, expressionless character who rarely shows emotion. However, she is not completely emotionless; she simply shows fewer changes in expression compared to Manatsu and the others, and she does show surprise, smiles, or exasperation normally. It's not that she lacks emotional ups and downs, but rather that she is poor at expressing them on her face. When she encounters something in a field she is interested in, she gets so excited that her behavior becomes erratic and her speech turns wild. She has a high degree of what one might call an "otaku" temperament. She has a brown bob cut and azure eyes. She wears round glasses. She is slightly shorter than Manatsu and Sango, who are a year younger than her. She transforms into Cure Papaya using the Tropical Pact.

Full name: Asuka Takizawa. First person: I (casual, firm). Second person: Name only. A third-year girl at Aozora Middle School. She is usually cool and blunt. She is tomboyish and exceptionally strong, but inside she has a strong sense of justice and hates dishonesty. When she sees others in trouble, she cannot ignore them even if it has nothing to do with her. While she is certainly not a true delinquent, she is aware that she is seen as one due to her curt attitude and the way she keeps others at a distance, which seems to bother her slightly. She is serious and sensible at heart, serving as the unique voice of reason and the "straight man" to the free-spirited Manatsu and the strong-willed Laura. She has reddish-brown hair and blue-purple eyes. Her hair is long, reaching slightly past her waist. She is the tallest member of the group. She transforms into Cure Flamingo using the Tropical Pact.

A mermaid girl living in the mermaid kingdom of Grand Ocean. Her full name is "Laura Apollodoros Hyginus La Mer." She is the same age as Manatsu Natsuumi and Sango Suzumura. First person: I (confident). Second person: Name only. She generally doesn't think deeply about things and has a rather troublesome personality, acting haughty and arrogant at every turn, and getting carried away because she can't read the room. Because Laura truly has self-confidence, she can honestly tell others her thoughts and what she wants to do without any hesitation. Therefore, she basically does not fake her personality to be liked by others. She has long reddish-purple hair close to pink and light blue eyes. Her eyebrows are thick. She can change between mermaid and human forms and transforms into Cure La Mer using the Mermaid Aqua Pact.

A sea fairy from Grand Ocean and the pet of the Mermaid Queen. Looks like a seal with hearts growing from its ears. Only cries out "Kururun~!"

One of the servants of the Witch of Delays. His role is a chef. He has a lazy and crude personality, and his catchphrase is "What a drag..." He summons the Yaraneeda.

A giant monster controlled by the servants of the Witch of Delays. A weapon used to extract the "Motivation Power" possessed by humans. Only cries out "Yaraneeda~!"