The flute named "Nokaze" was passed down through the hands of Oda Nobunaga, Toyotomi Hideyoshi, Tokugawa Ieyasu, and then Ieyasu's sixth son, Tadateru. It has been preserved to this day at Teishoin Temple in Suwa City, Nagano Prefecture, where Matsudaira Tadateru rests. It is said that Ieyasu treated Tadateru as an abandoned child merely because his face was ugly at birth. Furthermore, when he met Tadateru at the age of seven in Keicho 3 (1598), he reportedly remarked, "His countenance is strange, resembling the youthful face of Saburo (Matsudaira Nobuyasu)." This son was later exiled and quietly ended his life while confined at Suwa Takashima Castle. Empathy for Tadateru, who lived such a life, became the motivation for writing this work. The title "Ethnologue" signifies something akin to a folk tale or popular legend.