Nero
About
Nero is an Anti-bird who decided to stay alongside Asta after encountering him at the beginning of the Magic Knights Entrance Exam.
(Source: Black Clover Wiki)
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It's later revealed that she is a human named Secre Swallowtail (セクレ・スワロテイル).
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Secre Swallowtail is the servant of Lemiel Silvamillion Clover, prince of the Clover Kingdom and the first Magic Emperor. She is transformed into Nero after sealing Lemiel into a statue.
Five centuries later, she decides to stay alongside Asta after encountering him at the beginning of the Magic Knights Entrance Exam, and is later accepted herself as a member of the Black Bull squad of the Magic Knights.
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