Ninniyis an invisible child who has become invisible after being mistreated for a long time. She comes to the Moomin family to perhaps become visible again thanks to their care. The invisible Ninny is proper, polite and, according to Moomin and Little My, annoyingly bad at playing. Everyone in the family tries to help Ninny in their own way. They give her security, teach her to play, challenge her to take her place and show her feelings. During her time with the Moomin family, Ninny changes and becomes more and more visible. The visible Ninny is strong-willed and full of emotions and surprises everyone with her ability to take action.
