Some people say that the 'Kokushi-koku' must be present-day Taiwan, which used to be a part of Baekje's territory in ancient times, and others say that, based on the Gishiwajinden (literally, an 'Account of the Wa' in "The History of the Wei Dynasty"), the 'Kokushi-koku' must have been a country located to the south of Wakoku (Japan) and ancestors of Joshi KOKUSHI were given one of the Baekje's territories, 'Kokushi-koku,' that was located to the southeast of Wakoku, as a reward for their conquering of Wakoku.
「黒歯国」は台湾であるとし、台湾は古代には百済の勢力圏に含まれたとする論や、魏志倭人伝を典拠に「黒歯国」は倭国（日本）の南にあった国で、黒歯常之の祖先は、倭国を平定し、その東南にあった「黒歯国」まで百済の勢力圏に含まれていたとし、それらの平定の功績から領地として黒歯の地が黒歯常之の祖先に与えられたとする論などがある。