Wajin (倭人, Wajin, literally "Wa people") is in the narrow sense, the old name of the ethnic group of the Yayoi people who lived in the Japanese archipelago. In the wider sense, an ethnic group that was mainly active at sea between Mainland China, the Korean Peninsula and the Japanese archipelago.In general the Wajin that established themselves on the Japanese archipelago became the Yayoi people, the ancestors of the Yamato people. The word "Wajin" also refers to related groups outside of Japan. The first secure appearance of Wajin is in "Treatise on Geography" (地理志) of the Book of Han (漢書). After that, in "Gishi Wajinden" ((魏志倭人伝), a Japanese abbreviation for the "account of Wajin" in the "Biographies of the Wuhuan, Xianbei, and Dongyi" (烏丸鮮卑東夷傳), Volume 30 of the "Book of Wei" (魏書) of the Records of the Three Kingdoms (三国志)), their lifestyle, habits and the way of society are described and by cultural commonality such as lifestyle, customs and languages, they are distinguished themselves from "Kanjin" (han people (韓人)) and "Waijin" (Wai people (濊人)). Descriptions about Wajin can be found in the Old Book of Tang (945 AD) and the New Book of Tang (1060 AD) Several linguists, including Alexander Vovin and Juha Janhunen, suggest that Japonic languages were spoken by Wajin and were present in large parts of the southern Korean Peninsula. According to Vovin, these "Peninsular Japonic languages" were replaced by Koreanic-speakers (possibly belonging to the Han-branch). This event was possibly the reason for the Yayoi-migration into Japan. Janhunen also suggests that early Baekje was still predominantly Japonic-speaking before they got replaced or assimilated into the new Korean society. Source: Wikipedia (en)