Yuni is one of the five main characters of Star☆Twinkle Pretty Cure, known for occasionally ending her phrases with "nyan." She's got a complicated life—by day she's a space idol named Mao, but she's also Blue Cat, a phantom thief operating in the shadows. Eventually she gains the ability to transform into Cure Cosmo.
Her whole personality stems from deep guilt. She couldn't save her home planet, Rainbow, and that failure weighs on her heavily. Because of it, she tends to keep people at arm's length, turning down help from friends and blaming herself whenever things go wrong. It's made her independent to a fault, though fans often note her kindhearted nature shows through regardless—she'll help anyone in need, friend or foe.
The Blue Cat side of her comes with baggage. She's got a stealing habit that never quite went away, as shown in episode 22, and she's clever about it too. Lala has said Yuni always gets what she's after. When she targeted the Princess Star Color Pen, she used fireworks as a distraction and even manipulated Madoka's plan with the star donuts to her advantage.
As Mao, she's the complete opposite on the surface—bubbly, cute, and friendly to everyone. It was all an act though, designed to keep her real identity as a thief under wraps. The contrast between her personas is pretty stark, but they all feed into the same person underneath: someone running from her past.
Content compiled by AnimeList.moe from publicly available sources.