Middle school student Mana Aida is recognized for her vibrant passion and gentle nature, particularly by her friends Rikka Hishikawa and Alice Yotsuba. During a school field trip, villains from the "Trump Kingdom" emerge from another world, creating giant monsters from the selfish desires of civilians to wreak havoc. While searching for a way to halt the destruction, Mana encounters "Cure Sword," a mysterious Precure warrior. As Cure Sword fights the monsters, Mana meets Cure Sword's fairy companions, who inform her that she too possesses the ability to transform into a warrior. When the invaders from the Trump Kingdom begin to outnumber Cure Sword, Mana joins the battle with determination. She partners with Sharuru, one of the fairies, and transforms into "Cure Heart"—the Precure of Love. In her efforts to ally with Cure Sword, Mana inadvertently draws Rikka and Alice into the conflict; each of them partners with a fairy ally to transform into "Cure Diamond" and "Cure Rosetta," respectively. Together, they fight against the Trump Kingdom invaders to protect the love in the world from destruction.