Manatsu Natsuumi, a first-year middle schooler who has just moved from Minamino Island to Aozora City, meets Laura, a mermaid from the undersea land of Grand Ocean. The Witch of Delays has drained Grand Ocean's people of their Motivation Power, and her Yaraneeda monsters now steal it from humans as well, so Manatsu becomes Cure Summer to fight back. Sango Suzumura, Minori Ichinose and Asuka Takizawa soon join her, and together they form the Tropical Club at Aozora Middle School. This manga follows the TV anime of the same name.