This study focuses on how the sound of /ga/ line in early modern Japanese (Edo period) was written in data in the Joseon Dynasty The consonant of /ga/ line characterized by nasal sound is regarded not as [g] but as [ŋ], and it is considered the standard sound in Modern Tokyo dialect. However, there have been voices of concern about whether the nasal sound of /ga/ should be reflected in learning contents for Non-Native Speakers of Japanese since the sound has vanished amongst the young generation. Then, how Koreans in the Joseon Dynasty recognized the nasal sound of /ga/ line when it was the standard sound? This study examines the names of Japanese places which include the sound of /ga/ line appearing in data in Joseon Dynasty. As it turns out, Koreans at that time denoted the nasal features of /ga/ line as ‘ㅇ[ŋ]’, the final consonant of the last syllable. However, ‘ん’ of ‘豊後, ぶんご’ was not marked in existing research since it was confused with the nasal sound feature of /ga/ line. There has not been any study that points out the fact. Moreover, the final consonants of Korean language were misunderstood as the nasal sound feature of /ga/ line by Japanese as well. As a result, it is assumed that the final consonant of Korean, ‘ㅇ[ŋ]’ and the consonants of /ga/ line sounded too similar to distinguish.