On a rainy day, a lady whom Lili has never seen before arrives at home. Her dad introduces her: her name is Mika, and she's his new "great friend". Little by little, she takes up more and more space, and Lili doesn't understand why. All their habits are disrupted! How can they be a family that way, after so much time spent just the two of them? And what relationship should she form with Mika, whom she has to know?