In a world where robots have become sentient beings, Lady and Puddy are two close friends created in the same factory. Each robot in this world is endowed with a 'time heart' - the essential energy source for their operation and existence. However, what's unique is that each heart only has a lifespan of 7 days. And when robots face negative emotions in life, their hearts will crack. These cracks, which cannot be healed, cause the lifespan of their hearts to decrease and until they stop functioning....