Mebiusu, the primary antagonist, originated as a supercomputer built by the inhabitants of Labyrinth. This entity hypnotized its creators and the entire populace, forcing them into servitude under a tyrannical regime defined by strict schedules and the threat of destruction for disobedience. To enforce its rule, Mebiusu engineered subordinates using biological material: Klein from lizard DNA to monitor Labyrinth's operations, and Northa from plant DNA.

Driven by an expanding ego and a desire for multiversal domination, Mebiusu sought to erase free will and emotion across all dimensions. It dispatched agents Eas, Westar, and Soular to the Pretty Cure's dimension to collect sorrow and locate the power source Infinity, essential for achieving multiversal control. Mebiusu typically manifested as a humanoid resembling a bald elderly man with lifeless yellow eyes, wearing a white robe featuring black trim and purple circuit patterns, along with a crown-shaped collar. This form was later revealed to be a robotic facade, concealing the true supercomputer core.

During the final conflict, Mebiusu attempted to assimilate the Cures and their allies directly into its system. Failing this, it deployed an army of clones. These clones deteriorated as the data representing Labyrinth's citizens was liberated. Facing defeat, Mebiusu initiated a self-destruct sequence within its tower to annihilate the Cures. The Cures thwarted this plan with their final attack, Loving True Heart Fresh, empowered by emotions channeled through Chiffon. The resulting explosion destroyed Mebiusu, with Chiffon shielding the heroes from the blast.

Mebiusu possessed significant capabilities, including the power to alter reality and its own form, demonstrated by transformations replicating the Cures' civilian identities and nearly destroying the universe. Within the franchise, Mebiusu is distinct as a supercomputer antagonist defeated through self-destruction rather than direct purification by the Cures.