The Twin Knights(1958)

Futago no Kishi

Once known as a skilled fencer who had masqueraded as a prince in order to succeed her late father, Sapphire is now happily married to her love Franz and queen of their combined realm. After she gives birth to twins, a boy and a girl who are now equal in the royal line of succession, however, a dispute arises among the courtiers and populace over which child is the true heir. When a whimsical cherub with a familiar face is unwisely summoned to settle the matter, he allows sheer luck to rule in favor of the boy.

Yet once Prince Daisy is whisked away by a cabal opposed to his ascension, the remaining Princess Violetta must embark on the same path her mother once tread to safeguard her family’s claim to the throne. Cross-dressing is hardly the end of it as she undertakes breathless adventures with a gypsy lass she meets—Emerald!

(Source: Kodansha USA)