Fuu-chan emerged as a surviving fragment of the primary antagonist Fusion, scattered across Yokohama after its defeat. This small, amorphous entity showed no trace of its origin's malice, instead behaving with childlike innocence. It formed an instant bond with Ayumi Sakagami upon her rescue. Communicating only through simple "fu" sounds, it gained its name. Instinctively driven to protect Ayumi's happiness, Fuu-chan interpreted her emotional distress in literal terms. Hearing Ayumi express frustration about her new city and school, the entity began absorbing people, objects, and living creatures—including a neighbor's dog and Ayumi's mother—to remove perceived causes of her sadness. This reflected a limited grasp of morality, prioritizing Ayumi's expressed wishes above all else. Fuu-chan's power to absorb energy defined its threat. During battles with the Pretty Cure teams, it assimilated their attacks, growing larger and stronger each time. This absorption allowed it to replicate specific abilities like super-speed and super-strength. Its malleable form could shift shapes, enabling mimicry of objects such as a bracelet for concealment. Ayumi's intervention became pivotal when she transformed into Cure Echo. Her emotional appeal reached Fuu-chan, clarifying her true desire for connection, not destruction. This realization severed Fuu-chan's link to Fusion's lingering malevolence, sparking its redemption. To ensure Ayumi's safety and halt the reformed Fusion entity, Fuu-chan transferred its accumulated power to the Smile Pretty Cure team. This act destroyed the remaining Fusion fragments but caused Fuu-chan's own dissolution. In its final moments, Fuu-chan conveyed an enduring presence within the city and Ayumi's memories. After its sacrifice, Ayumi found the confidence to form friendships, indirectly achieving Fuu-chan's original goal. While the entity ceased to exist physically, its influence persisted through Ayumi's personal growth. Later appearances were minimal, primarily featuring Ayumi without Fuu-chan's physical return. The character remains exclusive to this narrative, holding no substantive role in subsequent seasons, spin-offs, or other media beyond its referenced legacy.