In Heaven, the souls of unborn children are being prepared for their births. Tink, an inexperienced apprentice angel, accidentally gives a child who will be born female both a pink "girl's" heart and a blue "boy's" heart. When this is found out, it's too late to fix the mistake, so Tink is banished to Earth in a weak mortal body to watch over the twin-hearted child.
Meanwhile, in a vaguely medieval kingdom note , the King learns to his dismay that the Queen has given birth to a girl and due to complications, cannot have another child. Women cannot inherit the throne and the King knows that his closest male relative, Duke Duralumin, is a wicked man who would make the dim-witted Plastic his Puppet King to oppress the people. So the King pretends that Sapphire is a boy, with only a handful of close advisors knowing the truth.
Thanks to her dual nature, Sapphire is equally adept at male and female activities — even if the latter must be taught in secret. The story picks up in Sapphire's early adolescence, as Duke Duralumin steps up his attempts to prove the Prince to be a girl, and Tink finally finds Sapphire in the mortal world. And it's a good thing Sapphire has a new ally, as the Duke is not the only force that threatens the kingdom.
Ribon no Kishinote was created by Osamu Tezuka in 1953 and is one of the earliest best known Shōjo manga note . The original manga series ran from 1953 to 1956 and proved popular enough to be granted a sequel, The Twin Knights, starring Sapphire's daughter, Princess Violetta, on her search for her lost twin brother, Prince Daisy. During the '60s, Tezuka also made a TV anime adaption and an extended remake of the manga. Both versions followed roughly the original story up until close to its ending where they split off in their own directions. The new manga had Sapphire encountering the pirate Blood, the swordswoman Friebe, and the goddess Venus, all while overcoming the permanent loss of her male heart. The anime also played around with some of these ideas, but quickly put them aside in favor of a longer Story Arc involving a new villain, Mr. X.
The anime was broadcast in the United States as Princess Knight or Choppy and the Princess, the latter being at first the title of a short movie made by mashing together three of the episodes. Distribution of the American version was spotty at best, and it wasn't until 2012 that the show got a proper DVD release. The 60's manga has received an English language two-volume collected release from Vertical inc in 2011 and a similar release of The Twin Knights saw the light of day in 2013.
The Princess Knight franchise consists of:
- The original manga series, which ran on Shōjo Club from January 1953 to January 1956.
- A radio drama series written by Seitaro Nakazawa, which aired on TBS Radio in 1955.
- The Twin Knights, a sequel which ran on Nakayoshi from January 1958 to June 1958.
- The second manga series, which ran on Nakayoshi from 1963 to 1966.
- The third manga series, which ran on Shōjo Friend from April 1967 to April 1968.
- A 52-episode anime series, which was produced by Mushi Productions and aired on Fuji Television from April 2, 1967, to April 7, 1968.
- Princess Knight: The Musical, which was produced in 2006 by Morning Musume with an all-female cast, aided by the Takarazuka Revue.
Princess Knight provides examples of:
- Feminist Fantasy:
- Girls can't inherit the throne in this setting but due to a quirk in the Magical Underpinnings of Reality, Sapphire can.
- The Twin Knights: Silverland's society has progressed enough that half of the kingdom is certain that Princess Violetta would be a better heir than Prince Daisy. Unlike in the prequel, Violetta's aptitude for sword fighting and other traditionally unladylike behavior isn't attributed to her having a male heart.
- Heir Club for Men: Deconstructed. Princess Sapphire is born into a kingdom where women cannot inherit the throne by the law. She's Raised as the Opposite Gender to keep the kingdom out of the evil Duke Duralumin's hand since he plans to rule from behind the scene through Plastic, the only other available heir. Subverted when Plastic becomes wise and gives women the right to inherit the throne.
- Heroic Sacrifice:
- Blood retrieves a potion to save Sapphire's life at the cost of his own life. Although it turns out he brought it back just a few moments too late.
- Emerald intends to use a potion to save Violetta in The Twin Knights, but the mother wolf saves her in turn by taking her place.
- Princess Protagonist: Princess Sapphire, the heroine, is a "two-hearted child" who was raised as a boy but has both male and female characteristics, who must save her kingdom from various enemies.
- Pink Girl, Blue Boy: Male hearts are blue, while female hearts are red.
- Raised as the Opposite Gender:
- Princess Sapphire is raised not only as a girl but also as a boy due to a law that only men can rule. It's complicated by the fact that she has the hearts of both a boy and a girl due to a mistake in Heaven.
- The Twin Knights: To try to convince the kingdom that Prince Daisy had be safely found, Franz ordered Violetta to alternate between living as a girl and a boy. Unfortunately, the Big Bad does catch on that the "prince" is never around when the princess is.
- Royals Who Actually Do Something:
- Plastic becomes a wise king immediately after either getting shot with divine lightning in the 50's manga or swallowing Sapphire's male heart in the 60's manga. In fact, the first thing he does is start to undo his father's evil deeds, then changes Silverland's outdated laws for the better and finally, paves the way to reinstall Sapphire as the righteous king. All what he wants in exchange is mercy for his father.
- Sapphire, among other things, heads a kingdom-wide revolution to get the women equal rights.
- The Twin Knights: Princess Violetta sets out to find her long-lost twin brother to free her parents from prison and stop the usurpers taking over the kingdom.
- Screw the Rules, I Make Them!: In Episode 22 of the anime, the King decides to abolish the rule that prohibits women from inheriting the throne but is abducted by bad guys before he has a chance to announce the decision and is presumed dead. The Queen believes Sapphire can pulls this upon being crowned King but it becomes a moot point as the Duke manages to expose Sapphire's true gender before she has a chance to change any laws.
- Stay in the Kitchen:
- Throughout the series, all the heroes decry the law stating that women can't rule as being misogynistic and outdated. Eventually, even the immature Plastic grows a pair and gets the parliament to unanimously agree to abolish that law, before giving Sapphire the crown and telling her she deserves to rule no matter what her gender.
- In the 60's manga, Tink reveals that only a magical flower from the realm of Venus can resurrect Sapphire. Sapphire's mother instantly volunteers, only for Franz to say, not unkindly, that she should stay in the castle and he ought to go because men are more suited for adventuring.
- Trope Codifier: This series codified the "princely crossdressing heroine" trope that was later featured in The Rose of Versailles and Revolutionary Girl Utena.
- Wholesome Crossdresser:
- Sapphire pretends to be a boy out of political necessity.
- The Twin Knights: Princess Violetta is forced to disguise herself to convince the kingdom that her brother, Prince Daisy, is still around. Sapphire, who doesn't fondly remember her days of living as a boy, is immensely sorry to subject her daughter to the same fate, though Violetta holds up pretty well.
- Gender-Blender Name: Sapphire's son is Prince Daisy. Daisy is normally a girl's name.
- Missing Child: Sapphire and Franz are terrified when they learn that their infant son has disappeared. They have the castle searched from top to bottom for him, and even search the moat.
- Peaceful in Death: The corpse of the mother wolf is found with a peaceful smile on her face.
- Arranged Marriage: Madame Hell schemes to rule Goldland by marrying her daughter, Hecate, off to Prince Franz.
- Fantasy Kitchen Sink: Apparently, the Abrahamic God and the Greek gods exist in the same universe.
- Good Hurts Evil: Crucifixes and other holy items cause great pain to demons.
- Lady Land: Black Pearl Island is a female-dominated kingdom, where any man coming is enslaved to draw water, work in the fields, and cut down trees.
- Lost in Translation: When Sapphire aids Friebe in combat, Friebe calls Sapphire out on how confusing it is to refer to herself with the masculine pronoun "boku". The English translation replaces it with Friebe calling Sapphire's declaration of protection confusingly masculine.
- No Ontological Inertia: Madame Hell is reminded at one point her flesh-to-stone spell will be reversed if she dies. Sadly, this also applies to Hecate because Hell created her with magic.
- No Woman's Land: In Silverland, women aren't allowed to vote or divorce and are considered inferior to the men. In fact, one of the driving conflicts in the series is that Princess Sapphire is born a girl and thus is ineligible for the throne. Subverted at the end when Plastic becomes The Good King, gets all women in the kingdom equal rights and gives Sapphire the crown.
- Post-Climax Confrontation: Once Madame Hell and Duke Duralumin are out of the picture, Venus serves as the final obstacle of Sapphire's and Franz's love.
- Real Women Don't Wear Dresses: Subverted. While Princess Sapphire and Friebe do their best ass-kicking while in masculine clothes, Sapphire learns to fight without her male heart, feels far more comfortable in feminine attire and it's implied that this is the way that's best for her. Friebe, meanwhile, is almost always seen in her armor, but wears a dress and brags about her ability to cook and sew as a selling point to convince Sapphire to marry her. Needless to say, none of their feminine traits stops them from being heroic and getting stuff done.
- Taken for Granite: Madame Hell turns Sapphire's mother and Gammer, then lots of people in the vicinity of the royal castle of Silverland, into stone.
- Bones Do Not Belong There: In one episode of the anime, a whale makes an appearance on-screen and eats a bunch of different creatures. One of them is a jellyfish. After eating it, he spits out its skeleton.