Because there is no historical material proving his birth date and the first half of his life is mostly unknown, there is no one else whose origin is so mysterious as that of Masashige, although he is highly well-known in Japanese history.
生年に関しての確実な史料は存在せず、正成の前半生はほとんど不明で、日本史上きわめて有名でありながら出自がこれほど謎に包まれた人物はほかにいないといわれる。