The phrase "mysterious girl" refers to a girl or woman who has an air of secrecy or enigma surrounding her. She may be intriguing or hard to understand, making her a source of curiosity and intrigue. Full definition
What can I say about me... I am very mysterious girl.. (loveawake.com)
Further details were also revealed: the game world has boundaries and is not spherical, as no one knows what lies beyond the sea; the aforementioned mysterious girl, Noi, emerges from one of the ruins falling from the sky; gameplay and battle systems have been adjusted in response to feedback about prior games» slow pacing; and boss fights were apparently one of the first things the staff designed. (randomnpc.com)
Further details were also revealed: the game world has boundaries and is not spherical, as no one knows what lies beyond the sea; the aforementioned mysterious girl, Noi, emerges from one of the ruins falling from the sky; gameplay and battle systems have been adjusted in response to feedback about prior games» slow pacing; and boss fights were apparently one of the first things the staff designed. (randomnpc.com)