Based on the book of the same name by Alexander Dermansky.

Girl Sonya lives on the outskirts of the forest. She goes to school, learns to play the flute, takes care of her grandmother, but she lacks friends. When the boredom becomes excessive, the pink monster Chu appears. They immediately become friends, but their joys do not last long - the other two monsters pick up a new girlfriend. Sonya decides to find Chu and goes to the forest, where she finds herself in a world of unusual monsters playing musical instruments. Will Sonia return her friend Chu?