Miruru is seen in some scenes in the movie, has more of a heart than the other members of her group. Her intelligence was rivaled with Kururu. She also seems to be able to transform into Nazca.

Her name Miruru is possibly from Mirara of the first movie, since Miruru is the key to the third Kiruru.

Miruru is a pink, blue-eyed Keronian resembling a fennec fox. Her pink hat has pointed ears. The edges of the ears are striped white. Her yellow hair hangs out of those ears. Her symbol is a blue, upside down triangle. She has a short white fox tail. She wears a shirt with long sleeves.

In her key form, it bears very resembles to Mirara's key form except its much smaller and short and her ears are still exposed.

(Source: Keroro Wiki)