English: The rectangle outlines the Japanese term mono no fu no michi (武士の道, way of the warrior/samurai), the native-derived synonym for the Chinese-derived word "Bushido", as found in the book Koyo Gunkan (甲陽軍鑑) by Kōsaka Masanobu - 1616 CE. Known as the first historical reference to "Bushido" in the history of Japanese ethical writings, it is regarded as an indispensable document for understanding the spirit of the samurai as formed during the Warring States period and compiled then in the early Edo period.