Prince Justin is a minor character who appears in the books and movie. In the books, he is the brother of the King of Ingary, while in the movie, he is the heir to the throne of the neighboring kingdom. He is described by his brother as a brilliant general, and the King does not feel safe going to war without at least either he or his Royal Wizard. He has a tendency to be cursed.
Simply referred to as "The Prince," he is the prince of a neighboring kingdom to Ingary who was cursed into existing as a turnip-headed scarecrow , with a tendency to get caught upside-down and helpless. The kingdom thought the Prince had been kidnapped by Ingarians, and declared war on them. Though Howl Jenkins Pendragon and the Witch of the Waste can see through the spell, his true identity is only revealed to Sophie Hatter and Markl at the end, when a kiss from Sophie breaks the curse. He appears to have fallen in love with Sophie, though she is in love with Howl. Free of his curse, he returns to his home to help negotiate a truce with Ingary.
Some time before the beginning of the story, Prince Justin goes to The Waste to search for Wizard Suliman, who had been creating a garden at its border when he disappeared. The finding spell he buys from Mrs Fairfax brings him to the Chipping Valley, and into Upper Folding, all the way to Howl's Castle. However, the spell begins pointing in two directions, and he gets lost. He buys another finding spell from Michael Fisher, Howl's apprentice, which turns out to be a dud. He buys another finding spell from there, which leads him to the edge of the Waste.
The Witch of the Waste captures him here, and uses parts of his body for her creation, combined with Wizard Suliman. The leftover parts are used to create a servant with little memory who follows her around called Gaston. However, when he disobeys her in the hat shop a few days after May Day, she transforms him into a dog and leaves him tied in the hills outside Market Chipping. He is later freed by a cursed Sophie Hatter on her exodus from Market Chipping, and runs away into the hills to Mrs. Fairfax's house where he remembered stopping by as Prince Justin.
While it is difficult, the dog-man, now named Percival, is able to transform back into a person long enough to ask Lettie Hatter for help. For some time, he stays with Lettie and Mrs. Fairfax, changing every so often back into a person. Every time, he changes back into a different kind of dog, and it is becoming more and more difficult to change, and he can stay a man for less and less time.
Eventually, he is sent to look after Sophie when Lettie learns she is now living with Howl. He asks Sophie not to tell Howl that he is a bespelled man, and becomes part of the family for some time, living with them as they go into hiding from the Witch of the Waste, who has put a curse on Howl.
Because of an imminent war with Strangia, the King of Ingary names Howl as his Royal Wizard to replace Wizard Suliman and orders him to search for Prince Justin, which he had already been doing in his own way since his disappearance.
Howl of course eventually discovers the cursed dog-man, and becomes angry with Sophie for not telling him. Lifting the curse, Percival is now himself again. Though he claims he does not remember much, when he is alone with Sophie, he explains that he worked for a bit with the Witch of the Waste, that he was there the day Sophie was cursed, and that he has been staying with Sophie's sister. However, he still does not remember anything beyond coming into service with the Witch of the Waste as Gaston.
Once the Witch of the Waste and her Fire Demon are destroyed, Howl is able to separate the bits of Prince Justin from Percival and the body the Witch had been creating to recreate him. The Prince returns to the King of Ingary, his brother, to report on what has happened and to help him prepare for the coming war.
Castle in the Air
After the war against Strangia has been won, Prince Justin is organizing men to search for Princess Beatrice of Strangia, Justin's intended, who has run away to avoid marrying Prince Justin. A djinn, who is later revealed to be Hasruel, appears before him, and declares that because Ingary won the war against Strangia because of unfair use of magic, he has kidnapped the Princess Beatrice, and curses Prince Justin, taking away his memories and making him believe he is a Strangian soldier. Prince Justin begins to steal from other men, and often flashes his coins everywhere to get men to attempt to rob him so that he can rob them.
He meets Abdullah's aquaintance at a tavern in Ingary. After Abdullah follows him as he lures two men into trying to rob him, and he and Abdullah manage to win a fight against them, they travel together through the mountains to Kingsbury. In the mountains, the soldier finds a mother cat and her kitten, who he names Midnight and Whippersnapper, and dots on them and thus they join the soldier and Abdullah on their journey to Kingsbury.
In Kingsbury, Abdullah leaves the soldier in an inn with the genie and the flying carpet. The soldier, tempted by the reward Abdullah has said there will be if Princess Valeria is saved from the djinn, orders the genie to wish him to the Castle in the Air. Unfortunately, Whippersnapper is also transported there, and the soldier is at a loss because Whippersnapper is no longer a kitten but a human baby. In the Castle, the princesses find him and disguise him as the Jharine of Jham. Another princess takes charge of the baby, feeding him milk from a bottle.
When Abdullah and Sophie arrive at the Castle, Sophie yells at the soldier for taking Morgan with him after the djinn. The soldier tries to explain, but Sophie does not want to listen. When Morgan begins to cry, Sophie finally allows him to explain. After the calm is restored, the princesses, Abdullah, Sophie and Jamal the cook begin to plan to overpower the djinns. The soldier threatens to betray them to the djinns and become their guard if he is not given a Princess to marry. Grudgingly, several princesses offer themselves but the soldier chooses Princess Beatrice, much to her astonishment. Beatrice says that she is not pretty, but the soldier says that he would rather have a princess who will stand by him no matter what and who can darn, rather than a beautiful fragile princess.
After the djinns are defeated, the enchantment on Prince Justin is broken, and he remembers who he is. He admits to Beatrice that he is really Prince Justin, but has been under an enchantment. He also realizes that he will have to do something about the Strangian soldiers wandering about Ingary. After the Castle comes back down to Earth, Justin stops all his complaints about having to marry Princess Beatrice, much to his brother's delight. Justin finds out that the King thought he had walked off in a huff after an argument over him having to marry Beatrice and hadn't even begun to worry about him. Because he is so pleased at Justin and Howl's return, the King orders a double wedding for Abdullah and Flower-in-the-Night (the new Ambassadors of Ingary), and Prince Justin and Princess Beatrice.
Later, Justin becomes monarch of Strangia alongside Beatrice, and the two are known as King Justin and Queen Beatrice.
- While never named, it is likely that the "neighboring kingdom" the Prince comes from in the movie is really Strangia, which lies along the border and is at odds with Ingary, eventually going to war with them.