Ego Ego, an artificial life form crafted by Gashuin Sarena to advance virtual dream research, begins as a white fox-like entity adorned with red markings beneath black eyes and a green bud on its back. Its form evolves dramatically: first into a towering anthropomorphic fox after assimilating a Miracle Flower, then into a humanoid figure with dark foliage-textured skin, pale limbs, and vibrant flower-like red hair upon merging with Kaguya, Sarena’s adoptive daughter.

Fueled by envy toward Kaguya, who garners more of Sarena’s affection, Ego Ego rebels against its creator. Abandoning obedience, it pursues dominance by seizing Dream Buds—vessels of human aspirations—and imprisoning members of the Yes! Pretty Cure 5 GoGo! team to drain their energy. This quest peaks when it absorbs the Miracle Flower, transforming into a colossal force intent on subjugating the City of Dreams.

In its final clash, Ego Ego merges with Kaguya, overpowering both the Healin’ Good and Yes! Pretty Cure 5 GoGo! teams. The united Cures unleash the "Healin’ Good Dream" attack—a rainbow-infused butterfly beam—that purifies Ego Ego, reverting it to its primal form. Overcome with guilt, it apologizes to Kaguya, acknowledging its misdeeds. Despite repeated defeats, its regenerative abilities render it tenacious, earning labels like "immortal" and "stubborn."

Ego Ego’s bond with Sarena fractures, shifting from servitude to bitterness, while its rivalry with Kaguya softens into mutual understanding through empathy. The arc closes on redemption, underscoring forgiveness and the peril of ambition untethered from compassion.