Osamu Tezuka's Princess Knight, originally known as Ribbon no Kishi in Japan, sounds like a pastiche of Disney princess movies. Sapphire is a headstrong princess who laments her current life and longs for the freedom to be what she always wanted to be. There's the prerequisite evil uncle who's constantly plotting to take over the kingdom, and an evil witch who yearns to steal Sapphire's heart for her own. What sets Princess Knight apart from typical Disney fare is Sapphire's plight. Born in a kingdom where only male heirs can succeed the throne, Sapphire must pretend to be a prince in public, while keeping her true identity a secret.
Today, Princess Knight is an integral piece of manga history. It's considered among the first serialized shojo (girls' manga) adventure works, emerging in a landscape where girls' manga were largely composed of comic strips and guides to good behavior. Female characters with secret identities are still a staple in shojo manga, and both Sailor Moon and Revolutionary Girl Utena can easily trace their lineage back to Sapphire. Princess Knight is also noteworthy for its unique take on gender identity, but while the manga depicts a female-identifying character being just as good as her male counterparts, Tezuka fails when he suggests that her strength stems from her "boy's heart."
Let's take a closer look at the weirdness of Princess Knight's gender politics.
Gender identity is predestined, except when it's a mistake
Princess Knight begins way up in Heaven because that's where all good fantasies start. God and his angels are busy getting human babies ready for birth. Gender is assigned to each baby by feeding it a heart. Blue hearts will create boys and pink hearts will create girls. One mischievous cherub named Tink decides to feed a baby a blue heart before God feeds it a pink heart, and hijinks ensue. A baby with both boy and girl hearts? Inconceivable! God goes ballistic on Tink and orders him to keep an eye on that baby's birth. If the child is indeed born a girl, as God wished, Tink must retrieve the boy's heart because who knows what mayhem might occur otherwise?
Tink arrives on Earth and discovers that the baby is indeed a girl, but the situation surrounding her birth makes retrieving the boy's heart complicated. Sapphire is born to the royal family of Silverland, where leadership must be passed on to a male heir. If word got out that the new royal infant is a girl, then the kingdom would pass to the son of evil Duke Duralumin. The royal family decides to keep Sapphire's true gender a secret, and thanks to Sapphire's boy heart, she is able to take on all manner of princely duties with no one outside of the castle aware of her real identity.
Princess Knight assumes that gender identity is chosen by a supreme deity, which seems like a nice, fairy-tale way to explain that you are born instinctively knowing what gender you are. But Sapphire's situation mangles this by making her gender identity a cosmic mistake. God doesn't make mistakes, but some of His minions might, even though He created those minions, and the minions in charge of something as important as gender shouldn't try to shove hearts into babies without God's consent first.
Shouldn't there have been more fail-safes for this process? Not to mention the very real existence of gender fluidity which would make Tink's mistake and God's anger moot. One could argue, of course, that this manga was written in the 1950s, and most people back then couldn't conceive of more than two genders. But readers are much more aware today, and the whole crux of Sapphire's conflict now feels a bit silly and trite.
Sapphire must remain a prince because ... reasons?
The royal family of Silverland announces that the new heir is a prince, which staves off the evil Duke's political aspirations, and Sapphire is raised, in public, as a boy. She's given boy's clothes to wear and she's taught all sorts of stereotypically "manly" things, like how to fight. However, Sapphire spends a lot of time lamenting the fact that she has to pretend to be a prince. While she seems to be the perfect prince in public, in private she loves to wear frilly dresses, sing, pick flowers, and talk to the various woodland creatures she's befriended.
Yep, she's basically a Disney princess who has to disguise herself as a prince.
Tezuka never gives a decent explanation for why Sapphire must continue with her ruse. Silverland doesn't even have a magical curse on it or anything that might physically stop a female heir from leading. If the kingdom can only be led by a male heir, and Sapphire's father is the king, then shouldn't he be able to change the law, because he's the king?
The only thing in Sapphire's way is a law, and laws can change. There's now a precedent for this in real life, with Japan's own imperial family and continuing debate over whether female heirs should be able to ascend to the throne. Again, the reasons for Sapphire's predicament ring a little hollower in modern times.
Sapphire's agency is punished
Throughout the course of the manga, Sapphire is a character that things happen to, not a character who decides her own destiny, which is strange for someone purported to be a headstrong young girl. It seems that when she decides to do something solely for herself, she messes her life up even more.
One early example is a Cinderella-like meeting with her destined handsome prince, Franz Charming. (Yes. Really.) Sapphire sorely wants to attend the annual carnival and dance the night away, but she's shackled by her responsibilities as the prince. Secretly, she asks her mother and her nurse for help. They give her a fabulous makeover, a lavishly ruffled ball gown, and a long blonde wig to hide her short, dark locks. Sapphire is finally who she wishes to be, at least for an evening, and she meets the prince of her wildest dreams in the form of Franz. Sapphire and Franz hit it off immediately, but she eventually has to rush off, leaving behind only memories of the "flaxen-haired maiden" whom Franz will continually pine for throughout the rest of the series.
It doesn't help matters that Sapphire, in her prince guise, is Franz's arch-enemy. Their two kingdoms are on hostile terms with each other, and thanks to some top-notch conniving by Baron Duralumin, Franz is wrongly accused of murdering Sapphire's father, the king. Sapphire, in her female guise, rescues Franz from the dungeon, but then she disappears again, leaving Franz to continue pining away for her, in her female identity, while perpetually hating Sapphire's male identity.
Sapphire just can't catch a break.
Gender roles are rigid for Sapphire, but not for anyone else
With her dual hearts, Sapphire appears to embody a "complete" person. She's adept at fencing, archery, and horseback riding, and her feminine side embraces dancing, music, and pretty things like flowers. However, strange things happen when her boy's heart is removed from her. With only a female heart to guide her, she becomes "weak," both literally and figuratively. She's passive and unable to fight back against an opponent that she'd easily defeated when she had her boy's heart. Sapphire, without her boy's heart, is initially useless. Eventually, she does find strength while possessing only a girl's heart, but it's strange to conceive that power and courage can only come from masculinity.
This wouldn't be so frustrating if Sapphire were the only female character who had traditionally masculine tendencies, but this isn't the case. Further along in the series, Sapphire meets a noblewoman named Friebe, who can buckle swashes against pirates and appears to have no qualms about her "masculine" behavior. She still considers herself a woman, and yet she can fight and go on adventures while in the possession, one can assume, of only a female heart.
It seems like Tezuka wants her to be the counterpoint to Sapphire. She is everything that Sapphire can be, even without the boy's heart. Through Friebe, Sapphire can see that strength can come from a girl's heart. Even female characters who are portrayed as demure and weak are depicted as being able to rise up and fight (albeit with unconventional weapons like brooms) when needed. Why, then, should strength be associated with masculinity and grace with femininity?
Sapphire's happy ending is oh so heteronormative
If gender is performance, then Sapphire has been performing in public for most of her life, and that was only in service to her audience, and not to herself. She grew to hate her performances because she felt like she was losing touch with her true self, her feminine self. She was never allowed to act female until her boy's heart was removed. Only then is Sapphire free to follow her female desires in earnest, expressing the love she feels for Franz and marrying him.
Some might not think of this as a feminist ending. After all, Sapphire's just settling for the traditional gender role for women. But Sapphire chooses her prince and chooses to be with him, so her agency is assured. She spent so much of her life hiding what she truly was, and now she finally is able to embrace being a young woman in love.
But viewed today, Sapphire's happy ending is disappointingly heteronormative. She chooses to be with her prince, true, but why must she lose her boy's heart before being able to be with him? What couldn't a dual-hearted Sapphire be both masculine and feminine and allowed to marry the prince and have kids? It would've sent a message that love transcends gender roles, but it probably would've been too radical an idea for a ‘50s manga.
Perhaps Princess Knight is best understood as a proto-feminist work. There are some incredible ideas within the narrative about the roles of women, and what should be considered masculine and feminine, but sometimes Tezuka fails his main character and gives the best female roles to the supporting characters. It's a little disheartening to see Sapphire be upstaged by someone like Friebe, but Princess Knight is still important, and it lay the groundwork for many beloved female manga and anime characters to come.