UFO Princess Warukyure, also known as UFO Princess Walkyrie, follows a princess from outer space who accidentally crashes on Earth, where Kazuto is desperately trying to keep his grandfather's public bath running. Due to the circumstances, Kazuto receives a part of Princess Walkyrie's soul, which forces her to stay with him. But that is not the only problem... because her soul has lost strength, the princess transforms both mentally and physically into a little kid!