Otto and Marta, a chubby German brother and sister, find themselves alone one summer afternoon, their parents out shopping. Marta, always the adventurous one, suggests a game of roleplay to pass the time. Otto, initially hesitant, agrees, and they retreat to their shared bedroom. Marta, dressed in a revealing schoolgirl outfit, begins to tease Otto, running her hands over his chest and whispering naughty suggestions. Otto, now fully aroused, plays along, pushing Marta onto the bed and hiking up her skirt to reveal her wet, eager pussy. They spend the afternoon exploring each other's bodies, their taboo desires unleashed, until the sound of their parents' car pulling into the driveway forces them to quickly separate.