Commanded by the elite Phantom Empire commander Black Fang, Saiarks act as the primary antagonists in "Eiga HappinessCharge PreCure! Ningyō no Kuni no Ballerina." These monsters physically manifest from human despair, specifically crafted to sustain the illusion of the Doll Kingdom and trap its inhabitants.

Black Fang deploys distinct Saiark variants against the protagonists. A Windmill Saiark falls to Cure Lovely's Pinky Love Shoot. Bee Saiarks ambush Seiji Sagara, cocooning and transforming him into a doll. Guardians resembling stuffed animals, including a Teddy Bear and Stuffed Rabbit, also appear within the kingdom.

Differing from their television counterparts, these movie Saiarks possess no environment-altering powers. They serve solely as direct combatants and psychological weapons. Their creation stems directly from Black Fang exploiting the despair of Tsumugi Orihara after he stole her ability to dance. The Saiarks fuel the Doll Kingdom's false paradise, ensuring Tsumugi remains isolated from reality.

While their scarves typically denote their summoner in the series, aligning with Black Fang's elite Phantom Empire affiliation, the film does not specify their color. The Saiarks' defeat becomes a key turning point; Tsumugi reclaiming her hope reverses her despair, stripping Black Fang of his power and enabling the Cures to destroy him.