Chacha is the eldest child of the Kiseichuu Queen, whose alien race invades Earth to drain human H-energy. A rare mutant occurring once per millennium, she displays distinct cat-like features and vulnerabilities, including sensitivity to catnip, making her biologically closer to felines than standard Kiseichuu.

Unlike her species, she lacks the ability to absorb H-energy. Instead, she generates potent pheromones transmitted via bodily fluids, sweat, or hair contact. These pheromones drastically amplify human sexual arousal (H-energy), heighten physical sensitivity, and can temporarily overwhelm or incapacitate recipients. Biting injects concentrated pheromones, triggering a "Beast Mode" state that grants enhanced speed and feral attributes but causes loss of rationality.

Initially imprisoned and reviled by the Kiseichuu for her anomalous abilities, she gained freedom after intervention by Kirara Hoshino and Retto Enjō. Following her rescue, she joined Retto's group and declared allegiance to HXEROS, formally renouncing her species during a confrontation with her mother.

Her personality reflects innate kindness and eagerness to assist, though unfamiliarity with human social norms often leads to unintended disruptions. She exhibits playful flirtation toward Retto and finds amusement in his accidental intimate encounters with teammates. Despite combat limitations, her pheromone amplification proves strategically vital, significantly boosting HXEROS members' power during engagements.

Chacha possesses additional abilities:
- Transformation: Allows mimicry of human appearances, clothing, animals, or objects like stuffed toys or XERO suits.
- Assimilation: Enables absorption and control of organisms by taking over their bodies.
- H-energy sensing: Detects and measures H-energy levels.