(In the explanatory note of the chapter Suetsumuhana in "The Tale of Genji," it was written that, Sengaikyo says there is a black-teeth country in which the women practice the custom of dyeing their teeth black.)
（『源氏物語』末摘花の注では「歯黒山海経云東海有黒歯国其俗婦人歯志黒染」とある。）