Washu was the fifth woman to appear in the series. A genius who is known through out the galaxy as a feared mad scientist. Exiled because of her evil intentions, Washu was imprisoned for all eternity in a crystal like capsule that crashed down to Earth thousands of years ago. The people of earth, sensing the evil that lurked inside the capsule, they concealed the "demon", as they believed, in a cave and built what is now the Masaki shrine. A few thousand or so years later, in present times, Washu was released after Ryoko broke the seal that held her for so long.
Washu isn't really a mean, hostile, and evil demon, but her inventions usually do cause trouble in the Masaki house hold. After her release she automatically took refuge in the Masaki home being the fifth addition to the family. She hardly ever travels away from her lab (except for meal times) which is located in the broom closet downstairs. She built a different dimension inside so that it was completely transformed into a huge laboratory.