As the pronunciations are given using Chinese characters, they are difficult to interpret, but several of those from central Korea, in the area south of the Han River captured from Baekje in the 5th century, seem to correspond to Japonic words.

[7][8] Characters like 買 and 忽 presumably represented pronunciations based on some local version of the Chinese reading tradition, but there is no agreement on what this sounded like.

[26] In a review for Korean Studies, Thomas Pellard criticizes Beckwith's linguistic analysis for the ad hoc nature of his Chinese reconstructions, for his handling of Japonic material and for hasty rejection of possible cognates in other languages.

[27] Another review by historian Mark Byington casts doubt on Beckwith's interpretation of the documentary references on which his migration theory is based.

[34] Alexander Vovin has suggested Japonic etymologies for several words and placenames from southern Korea appearing in ancient Chinese and Korean texts.

Two of these include a suffix *-mietoŋ ⟨彌凍⟩, which has been compared with Late Middle Korean mith and Proto-Japonic *mətə, both meaning 'base, bottom' and claimed by Samuel Martin to be cognate.

[41][42] Chapter 81 of the Chinese Book of Sui (656) mentions tammura (躭牟羅), an earlier form of the name of the kingdom of Tamna on Jeju Island.

The first character of the place name (神) cannot be read as gam/kam in Korean, but Vovin suggests that the first syllable was originally a word cognate to Old Japanese kami2 'deity'.

[46] Most linguists studying the Japonic family believe that it was brought to the Japanese archipelago from the Korean peninsula around 700–300 BCE by wet-rice farmers of the Yayoi culture.

[47][35] John Whitman and Kazuo Miyamoto associate Japonic on the Korean peninsula with the Mumun culture, which introduced wet-rice agriculture around 1500 BCE.

[48] Vovin and James Marshall Unger propose similar models, but associate Koreanic with iron-using mounted warriors from Manchuria.

[53][54] In contrast, Juha Janhunen argues that Koreanic expanded from Silla in the southeast, replacing Japonic languages in Baekje and the rest of the peninsula.