The book was written by Candidate Academician, Prof. and Dr. Jo Hui Sung of the History Institute of the Academy of Social Sciences who is the chairman of the History Society of the DPRK.

In this regard, the author told KCNA: In the last period, the study of the history of the early Korea-Japan relations had leaned toward Kaya (an old kingdom that existed in Korea from the mid-1st century B.C. to the mid-6th century A.D.) or Paekje (late 1st century B.C.-660) in many cases. With the discovery of data and research intensified, it was newly verified that Koguryo had exerted a great political and cultural influence on Japan. In particular, the Izumo area of Japan on the East Sea of Korea and its Yamato Asuka State in the sixth-seventh centuries were affected much by such influence. The book is aimed to tell about the facts in detail.

The book consisting of four chapters reviews the advance of Koguryo people into Japan and their settlement circumstances and distribution with geographical names, documents and archaeological data. It tells about villages and minor states built by Koguryo people in the area of Honshu Island and about the formation of power by those who advanced into the areas of Kawachi and Yamato.

Noticeable in the book is a fresh proof based on the deep study of geographical names, documents and archaeological relics and remains that ancient Takamatszuka tomb, unearthed in 1972, was built in the sixth century, not in the period from the late 7th century to the early 8th century the Japanese scholars has insisted so far.

Besides, the book refers to some aspects noticed in Koguryo's cultural influence on Japan like the origins of the tomb with salient parts at four corners and a group of tombs in Omuro of Shinano (now Nagano) Prefecture, the genesis of geographical name of Tokyo's Musashino and the derivation of Japanese soy sauce and soybean paste, matters in dispute among Japanese historians.