Gupi and his friends enter an empty, abandoned apartment in their building to deliver a cake, but when they pass through a closet in the room, they find themselves in a dark, gloomy, and different dimension. This new world is home to the palace of the King Who Never Smiles, whose sadness has spread throughout the realm. Realizing that because the king never smiles, all the people living in that dimension have lost their joy, the characters begin to try various methods to make the ruler smile and bring happiness back to the kingdom.
