Tart originates as a member of Dark Fall, serving Queen Desperia. This small, humanoid cat-like creature possesses pink fur, large ears, and a tail, with the ability to transform into a human form resembling a young girl with pink hair, wearing a distinctive outfit including a hat with cat ears.

Sent to the human world by Queen Desperia, Tart's primary mission is to locate and capture the powerful Rainbow Jewel. Tart manipulates events and targets the Pretty Cure teams to drain their power, which is linked to the Jewel.

During interactions with the Cures, especially in human guise, Tart begins experiencing unfamiliar emotions, like curiosity about human activities such as playing and forming friendships. Witnessing the Cures' unwavering bonds and determination to protect others creates internal conflict regarding Dark Fall's objectives.

A pivotal shift occurs when Tart witnesses the Cures risking themselves to protect innocent bystanders. This act profoundly impacts Tart, challenging loyalty to Queen Desperia. Tart ultimately chooses to rebel against Dark Fall.

In the climax, Tart intervenes to shield the Pretty Cures from Queen Desperia's attack. This act of protection results in Tart's apparent destruction.

However, as a consequence of this selfless sacrifice and the embraced positive emotions, Tart is reborn. Tart reappears as a very young human child, retaining pink hair but possessing no feline features or memories of the previous existence as a Dark Fall operative. This new human form signifies a fresh start.