Valkyrie is an alien princess that ran away from home and Crash landed her ship in to a bath house.
Valkyrie has two forms, child and adult.
Walküre in the original Japanese, after transferring part of her soul to Kazuto and becoming the small 8-year-old child, Valkyrie became very different than her original self, and even at times refers to herself as "Val". Fitting her age, she's extremely childish, show a strong interest in things like TV and manga. Even though she is incredibly attached to Kazuto, she becomes very loud and finds ways to wreck Kazuto's house in her child form. She also gets jealous easily, and often says things that are easily misunderstood by others, such as saying she gave Kazuto her "special thing". This young Valkyrie is always cheerful and has an adoring follower in Sanada, her maid. Valkyrie in her 8 year old form also calls Kazuto "Kazie" (in the English dub) which is one of the ways she shows her childlike crush on him, which is stronger in her adult form.
Heroine of the series and a princess from Planet Valhalla, in the Dolphin Constellation. Once Valkyrie learned that her father was planning a political marriage for her without her consent, she fled to Earth and crash landed on Kazuto's bathhouse. In order to save his life she had to give half of her soul to him, but that process turned her into an 8 year old girl. She can only regain her normal form by kissing Kazuto but it doesn't last long and she normally kisses him in order to protect him. She eventually develops deep feelings of love for Kazuto. Her powers include flight, energy manipulation and defensive shields, plus she gains the Key of Time at the start of the second season, which is capable of a number of things (though before, she already had an object that looked exactly like it). Oddly, early on she's able to use it her child form and adult form, but later only uses it her adult form. When it is later revealed that Kazuto is the one that she will marry, she is overjoyed, but it is difficult for the ceremony to take place since she keeps on reverting back to her child form. At the end of the 3rd season, due to a mishap with the Princess Mural, Valkyrie's older and younger selves split into two separate people. During the 4th season, Valkyrie's former classmates mistake her younger self to be her daughter, until she display knowledge about them convinces them she really is the younger Valkyrie.