Mermaid Princess of the Indian Ocean and keeper of the orange pearl.
She joins Gaito in his quest to take over the marine world after an incident bestowed her a dark power, turning both her orange hair and her orange pearl pitch black (though her eyes stay orange) and destroying her own kingdom.
That incident was a proposed rendezvous with Tarou, her secret human lover, in which he never showed up. In a fury, Sara unleashed a wave of power, destroying her kingdom and causing the wave which killed Kaito's parents and from which Lucia saved Kaito.
In the manga, Tarou actually arrived, but Sara's guardian found out about the relationship and insisted that he leave, convincing Sara that he had abandoned her.
