A 14-year-old girl from 2027 is transported to 1999 by a fairy, where she meets a detective-aspiring teen. When mysterious thefts occur, they transform into Star Detective Pretty Cure to solve crimes and protect their city using deduction.

Popular student Miyu Suzuki asks random questions to quiet classmate Yuusuke Tani. Despite their different personalities, love grows. After a misunderstanding leads to her confession, they begin dating.

Mermaid princess Lara defied her world for love, becoming human through a witch's potion. Unable to find true love, she dissolved into the sea. Two centuries later, she reawakens in Lake Biwa, resuming her quest for love.