In this research, I examined notation notation such as country name, formal name, person name etc in phonological system of ancient Japanese, especially Gisiwajinden, especially focusing on letters. Japanese customs and culture of the 3rd century is written in Gisiwajinden. Especially, proper noun is a notation of intrinsic Japanese sound of kanji, that is, a renting notation. The notation of Gisiwajinden's proper noun is written in total of 60 letters in 39 syllables. Compared to the pseudonym used in Gijiki, Nihonsyoki, Manyousyu, When expressing the same syllable using the same kanji, When using different kanji, character of kanji was sometimes different even if using the same kanji.
In this research, we focused on “升, 聲” to express syllables of “と”.
“升” can be confirmed in “彌馬升, 難升米”, “聲” can be confirmed in “伊聲耆”. Both characters that can be classified as a 書母 are used as pseudonyms of “と” although they are likely to be used as pseudonyms of the “サ” line.
This can be solved by Huang Kan’s “Characters such as 照2system belong to the 精system, characters such as 照3system belong to the 端system”. In other words, it means that the positive tooth sound is treated as a tongue head sound in the Old Chinese. This means that the 書母 belongs to 透母 in the Old Chinese, so it can express the “タ” line sound. Also, this is the conclusion that “聲” also holds as a pseudonym representing the syllable of “と”.