Elinor, a lonely and destitute orphan girl, accidentally finds a Starry Magic Necklace. Upon wearing it, she instantly transforms into a stunning princess and is forced to take the place of the missing Princess of Avalon in an arranged marriage with Prince William. Desperate to survive, she plans to steal money and escape, but finds herself protected step by step by the devoted prince. In the palace, she must hide her true identity, pass strict etiquette tests, and face repeated schemes from her former maid Cora, as well as assassination attempts from rebels. She falls into danger many times. As days pass, Elinor gradually loses her heart to the prince, but she is constantly tormented by the burden of her lies and the guilt of impersonation.
