平将門
The title "ninja" has sometimes been attributed retrospectively to the semi-legendary 4th-century prince Yamato Takeru. In the "Kojiki", the young Yamato Takeru disguised himself as a charming maiden and assassinated two chiefs of the Kumaso people. However, these records take place at a very early stage of Japanese history, and they are unlikely to be connected to the "shinobi" of later accounts. The first recorded use of espionage was under the employment of Prince Shōtoku in the 6th century. Such tactics were considered unsavory even in early times, when, according to the 10th-century "Shōmonki", the boy spy Koharumaru was killed for spying against the insurgent Taira no Masakado. Later, the 14th-century war chronicle "Taiheiki" contained many references to "shinobi" and credited the destruction of a castle by fire to an unnamed but "highly skilled "shinobi"".