Hiyori suffers overwhelming grief after her grandmother's death, crying every day without relief. To ease her distress, her father builds a humanoid robot named Wasimo, crafted to mirror the appearance of her late grandmother. This resemblance includes specific details like dentures. Wasimo moves at a walking pace described as faster than a snail yet slower than a rhinoceros beetle. However, when running, Wasimo demonstrates remarkable speed, capable of outpacing a bullet train.