Sapphire

Sapphire presents herself as a boy so she can inherit the throne and prevent Duke Duralumon from taking power. Refined rather than tomboyish, she is a capable swordswoman with a strong sense of justice and secretly fights crime at night as the masked Phantom Knight.

Later, Sapphire also goes about openly as a girl by wearing a blonde wig and posing as "the Princess," supposedly Prince Sapphire's sister. That identity lets her court Prince Frank.