RARA was living happily with her master when suddenly she was hit by a car in an accident. Although her body was repaired, her memory chip was damaged and her memories could not be restored. With all her memories gone, RARA returns to her master under a new name: HOTARU. Though she looks and sounds exactly like RARA, the fact that she doesn't remember him causes her master to treat her coldly. How will their relationship evolve under these circumstances?