UFO Princess Valkyrie is a 2002 manga created by Kaishaku (of Steel Angel Kurumi and Destiny of the Shrine Maiden note fame) for Square Enix's Monthly Shonen Gangan, it was later adapted by into an anime by TNK that same year.
The story is about magical princesses from outer space. One of said princesses, namely Valkyrie, lands her spacecraft on the Tokino Bath House, killing its current manager, the teenage Kazuto Tokino. So in order to save his life, Valkyrie gives him half her soul. Thus the obviously adult Valkyrie is transformed into a young girl who looks and acts like a child.
Valkyrie and her fellow princesses have magical powers. So whenever Kazuto and his crew encounter any problems, she is able to transform and protect him.
Aside from causing Kazuto and his sister Rika financial problems by damaging the bath house, Valkyrie has caused problems for her sister Hydra. Valkyrie ran away because she was supposed to marry a man she didn't love. Hydra, as the second oldest unmarried princess, is going to have to marry him if Valkyrie doesn't, so she goes to Earth and wreaks havoc trying to find Valkyrie. Eventually, she is stopped by Kazuto's shrine priestess neighbor and childhood friend, Akina Nanamura, who turns her into a little girl (like Valkyrie, but with her adult mind) so she is "easier to control". Also, Hydra crashed into Akina's shrine, and Akina keeps her around so she can "work off the damage".
Akina is also a childhood friend of Kazuto and has a secret crush on him, often putting her at odds with Valkyrie. So she and Hydra are sometimes partners in crime to cause problems for Kazuto and crew.
Later, Sanada, a catgirl maid of the royal family of Valhalla, the planet whence comes Valkyrie and Hydra, returns looking for Valkyrie. She is not shocked by Valkyrie's new appearance; in fact, she finds the new Valkyrie intolerably cute. Sanada takes her mission to protect Valkyrie to extreme lengths, including, for example, turning a bunch of ordinary girls who talk even indifferently to Kazuto, into mindless catgirl servants for the Tokino Bath House.
More crazy characters come along, including prima donna/diva/ditz Laine, Cloudcuckoolander Chorus, and the intolerably ruthless "older princesses".
The show is light (mostly) in nature and is kind of a slice of life show. There are four seasons, of varying length. The second season is more serious and dark than the others, mainly because of Valkyrie Ghost, a mysterious figure who appears to Kazuto.
Welcome to the crazy world of UFO Princess Valkyrie, where alien (though humanoid) princesses run wild and cause mass chaos among Earthlings.
Theme songs and insert songs are by Melocure and the background music was composed by legendary composer Kenji Kawai.
- A-Cup Angst: Akina, while she isn't exactly flat, but she really feel intimidated by everyone else's "perfect" size busts. Mentioning them is also her Berserk Button.
- Alien Princess: The titular Valkyrie, as well as her sister, Hydra, are Princesses of the planet Valhalla. Valkyrie crashes on Earth trying to escape an Arranged Marriage. And Hydra crashes on Earth trying to drag Valkyrie back to the Arranged Marriage so that she won't have to marry the guy, herself.
- Brainwashed: Catgirl servants. Pharm's servants. Seriously, there aren't interplanetary weapons treaties against ray guns that transform ordinary women into slavishly loyal servants to a foreign power?
- Breast Expansion: A scene in the second season where after Valkyrie makes a cookie bigger with magic. Just after that Hydra makes a joke about making Akina's breasts bigger. Guess what happens next. Good thing Akina wanted bigger breasts.
- Childhood Friends: A common tactic Akina uses to appeal to Kazuto is to try to leverage the memory of the time they spent together as children. Ultimately this doesn’t work.
- Cloudcuckoolander: Chorus. She thinks she's a robot and has also thought she is an alien. (Well, technically she's right about the alien part.)
- Descent into Darkness Song: 'Princess of December'. Starts out as a romantic song of eternal love and devotion, sung by the titular Valkyrie, only for it to be hijacked halfway through by her Shadow Archetype, Valkyrie Ghost, who turns it into a heart-wrenching song of loneliness and despair. It's one of the first hints that the Dark Valkyrie is actually a tragic figure, rather than the out-and-out villain she first appear to be. You can hear it here.
- Drives Like Crazy: Valkyrie, Hydra, and Pharm. But specifically, Laine. Who fortunately drives her motorcycle better than her saucer.
- First Girl Wins: Subverted somewhat. Though she has apparently "lost" to Valkyrie, Akina, in the last episode, enters a wish letter that will be granted by magical properties of Valhalla. Three people make wishes, but her letter is the only one not uncovered by little Valkyrie.
- Fusion Dance: Akina and Hydra are capable of fusing into a form dubbed Akidra, possessing their combined power and abilities with their personalities remaining separate allowing them to communicate with each other. The catch however is that they have to hate each other in order to do it and will defuse if they come to like each other too much.
- Harem Anime: Kazuto is surrounded by women. Whether they desire him or not is somewhat irrelevant (but quite a few do).
- In Medias Res: The first episode of the anime begins with Valkyrie and Hydra already regressed to childlike bodies, Sanada as Valkyrie’s caretaker and her catgirl task force acting as the bathhouse’s staff.
- Ironic Hell: Essentially, where Inarba sends a character if he/she has been bad. But only for a short time.
- Kick the Dog: Literally, seen with Little Val and Spot. Justified and averted because Children Are Innocent. Also, he's actually not a dog.
- Knight of Cerebus: Valkyrie Ghost, contrasting with the normally lighthearted nature of the series, stops all the comedy whenever she shows up, and her true nature adds to it.
- Leitmotif: Everybody who has a transformation sequence. Also Chorus.
- Magic Pants: Valkyrie and Hydra. Their outfits seemingly able to accommodate the change in size during transformation. Also, little Valkyrie does not wear pants (just a skirt) while the adult one does.
- Market-Based Title: When the anime version was released in English, ADV retitled it UFO Ultramaiden Valkyrie, the reason for that is because at the time, ADV had licensed quite a few series that had "Princess" in the title and stores were asking them not to license anymore series with "Princess" in the title because the weren't selling very well, this prompted ADV the alter the series' name.
- The Nicknamer:
- Rika, who calls Little Valkyrie "Valkyu".
- Also Little Valkyrie who calls people by cute variations of their names, like "Hydie" for Hydra and "Chorie" for Chorus.
- No Sense of Distance: Comet Sleipnir, just passing by Earth in the last episode, will visit Valhalla in 900 years since it's on the other side of the galaxy.
- Not Himself: Used ironically, as the past versions of Laine see a marked difference in the character of their future self. While in the past Laine also noticed that Valkyrie as a child didn't act like little Valkyrie at all.
- Official Couple: Kazuto and Valkyrie. Surprise.
- Onee-sama: Valkyrie to Hydra. Though this often seems cast aside as a joke or a phase Hydra went through, even though Hydra doesn't seem to prefer the male gender, though, besides Kazuto, there isn't much choice. Also, Valkyrie to Laine, in a flashback episode.
- Poor Communication Kills: Some of the earlier misconceptions about Kazuto and Valkyrie’s relationship are the result of little Valkyrie not telling people about their shared soul and instead referring to it as “The greatest thing a woman could ever get to a man” or something to that effect.
- Power of Friendship: Parodied, because Akina and Hydra have to actually become mad at each other in order to activate their Fusion Dance, and separate when they get along again.
- Shared Life Energy: When Valkyrie crashes on Earth, she accidentally kills Kazuto. She gives him half of her life energy to restore him, but this has the unintended consequence of de-aging her.
- Standard Snippet: A rather unique version of "Ride of the Valkyries" is often used during the series.
- Voluntary Shapeshifting: Laine's ability
- Morphic Resonance: While she is a capable Voice Changeling too, the two parts of hers she can't possibly modify are her breasts (she is somewhat well endowed) and her antennae thing which is also her "weak point" since pulling it means she will revert back. These are the only things that can give away her disguise, especially when she tries to put on a disguise as a male character.
- Glamour Failure: And if that wasn't enough, her extremely perverted and OOC behavior (by the impersonated character's standard) usually gives her away before Fridge Logic kicks in.
- Waif Prophet: Chorus. Even though most of what she says is nonsense, she is somehow able to predict the 12 Moons of Valhalla arc.
- World of Buxom: Out of the eight princesses, Chorus is the only one who isn't extremely ample, and that's because despite her height, she's actually one of the youngest if not the youngest of the princesses.