Published on April 17, 2019.
Using a Wikipedia entry on Mimana Nihon-fu as a point of departure, this piece examines the relationship between Wa and the southern Korean Peninsula through sources and evidence such as keyhole-shaped tombs, magatama, the Gwanggaeto Stele, the Nihon Shoki, and the Samguk Sagi.
It criticizes distortions produced by Korean nationalist historiography, the accommodation of some Japanese researchers, and the contradiction of Korean academia in citing the Nihon Shoki while rejecting only the theory of Mimana Nihon-fu.

2019-04-17
The oldest Korean historical text is the Samguk Sagi of the twelfth century, and because no ancient Korean historical texts exist, everything is quoted from the Nihon Shoki.

Mimana (みまな／にんな, to 663) was a region in the southern Korean Peninsula that existed in ancient times.
Overview.
The prevailing view is that it included the region centered on Geumgwan Guk, the successor to Guya Hanguk in the “Account of the Wa People” in the “Dongyi” section of the Book of Wei in the Records of the Three Kingdoms, which formed the northernmost extent of Wa on the Korean Peninsula, as well as Byeonjin and Byeonhan among the Samhan, parts of Jinhan, and part of Mahan, including what is now Jeollanam-do.
There is also a theory that it refers specifically to Geumgwan Guk, now Gimhae City in Gyeongsangnam-do, among the states of Mimana.
In the region that later became Gaya Hanguk, Geumgwan Guk, and then Mimana, Yayoi pottery completely different in style from earlier pottery began to increase sharply in the middle Yayoi period, the fourth and third centuries BCE, and this is regarded as the result of Wa people advancing into the region that later became connected to Mimana.
After the Second World War, the Mimana issue gradually came to be avoided for political reasons, but because the theory that the Gwanggaeto Stele had been altered by the Japanese Army, including the passages stating that Wa made Silla and Baekje its subjects, was denied and its source value clarified, and because a number of keyhole-shaped tombs unique to Japan began to be discovered in the southern Korean Peninsula, various views have in recent years been presented acknowledging the existence of governing rights, military command rights, and taxation rights by the Yamato court itself or groups deeply connected with it.
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The Japanese historian Takashi Yoshida criticized the generalization of Tanaka’s theory that the Nihon Shoki used the term Mimana as a collective name for the Gaya states, and argued that the use of Mimana in the Nihon Shoki, just as “Yamato” can indicate Yamato Province and at the same time all of Wa, referred simultaneously to Mimana Gaya, that is Geumgwan Guk, and to the whole political realm centered on Mimana Gaya.
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Mimana Nihon-fu.
See also “Mimana Nihon-fu.”
From around the 1960s onward, nationalist historiography spread on the Korean Peninsula, and as a reaction against positivism, claims were made that the direct rule of Mimana by the Yamato polity described in the Kojiki and Nihon Shoki was exaggerated.
In 1983, Professor Kang In-gu of Yeungnam University published a measured drawing stating that Songhak-dong Tomb No. 1 in Gyeongsangnam-do, with a mound length of 66 meters, was a keyhole-shaped tomb, but later Korean researchers proposed the view that it was not a keyhole-shaped tomb at all, but rather three round mounds of different construction periods that had accidentally overlapped.
However, there are suspicions that Songhak-dong Tomb No. 1 underwent alteration work in order to erase traces of Japan.
In relation to this, it has been pointed out that photographs taken in 1996 show a keyhole-shaped tomb, whereas photographs taken in 2012 show three separate mounds.
In the southwestern Korean Peninsula, discoveries of keyhole-shaped tombs have followed one after another, and so far eleven in Jeollanam-do and two in Jeollabuk-do have been confirmed.
Moreover, all of the keyhole-shaped tombs on the Korean Peninsula were built in the very limited period from the late fifth century to the middle of the sixth century, and they are known to exist in the western part of the Mimana region and at the southern tip of the peninsula, before Baekje moved south and advanced its annexations, and to be accompanied by Wa-type artifacts such as cylindrical haniwa, shell products from the southern islands, and stone chambers painted inside with red pigment.
Other circumstantial evidence indicating the sphere of influence of the Yamato polity includes large numbers of jade magatama excavated within the spheres of Silla, Baekje, and Mimana, though rare in former Goguryeo territory.
Before the war, Japanese archaeologists interpreted these as objects indicating the range of Yamato authority, but after the war a new interpretation was proposed that they had been transmitted from Korea to Japan.
However, because there is no jade source on the Korean Peninsula, because in ancient East Asia jade workshops have been found nowhere except around Itoigawa in Japan, and because recent chemical-composition testing has shown that magatama unearthed on the Korean Peninsula are the same as those from sites around Itoigawa, it has become clear that they were exported from Japan.
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Interpretations based on Korean nationalist historiography that denies positivism.
In contemporary Korea, in order to cultivate ethnic pride, the government and academic world are promoting nationwide a nationalist historical view that actively twists sources such as the Kojiki and Nihon Shoki, archaeological findings, the Gwanggaeto Stele, and the “Account of Wa” in the Book of Song.
In 1963, Kim Seok-hyeong presented the “theory of branch states.”
This claim holds that the inhabitants of the Samhan migrated to the Japanese archipelago and founded branch states according to their places of origin, specifically that Gaya people settled in Hiroshima and Okayama, and Silla people in the northeast.
The issue of Mimana Nihon-fu is interpreted as a dispute among these respective branch states.
This theory was criticized as nothing but self-contradiction because, while denying the Nihon Shoki, it accepted the Izumo myths, the myth of the descent of the heavenly grandson, and the tradition of Emperor Jimmu’s eastern expedition as historical facts, and from there drew the conclusion that such “branch states” existed within the Japanese mainland.
It gained no support at all.
Entering the 1970s, the Japanese researcher Hideo Inoue, who concurred with that line, argued that “Mimana Nihon-fu” was a designation found in the Baekje Hongi quoted by the Nihon Shoki, and that late-sixth-century Baekje, in trying to conciliate Wa, that is the Yamato polity, against Goguryeo and Silla, merely linked the “Wa” that in the Book of Wei’s account of the Han peoples had referred to the states of the southern Korean Peninsula with the polity of the Wa people of the Japanese archipelago, thereby giving only the impression that the power of the Yamato polity had extended to the southern Korean Peninsula from an early time.
He claimed that the actual text of the Baekje Hongi shows that Mimana Nihon-fu had no direct relation at all to the Yamato polity.
There can be no doubt that this Hideo Inoue too is one of the men being manipulated by the theory of dividing Japan.
Kim Hyeon-gu, a professor at Korea University and a scholar of ancient Japanese history, points out that although the Nihon Shoki says that Wa established Mimana Nihon-fu, ruled the southern Korean Peninsula, and while doing so carried away the culture of Baekje, Goguryeo, and Silla, Korean middle-school and high-school history textbooks do not explain the international relationships through which the cultures of Baekje, Goguryeo, and Silla were transmitted to Japan, but teach only that these three kingdoms conveyed culture to Japan.
Moreover, the stories said to describe the transmission of the cultures of Baekje, Goguryeo, and Silla to Japan are all quoted from the Nihon Shoki, because the oldest Korean historical text is the twelfth-century Samguk Sagi and no ancient Korean historical texts exist.
However, when Japanese scholars cite the Nihon Shoki and argue the theory of Mimana Nihon-fu, namely that Wa ruled the southern Korean Peninsula, Korean academia rejects it as unacceptable.
He points out that this is a clear contradiction, and that such a double standard may be one reason why Japanese academia looks down on Korean academia.

Interpretations based on Japanese historiography.
In Keyhole-Shaped Tombs and Ancient Japan-Korea Relations, edited by the Chosen Gakkai in 2002, Tadashi Nishitani argued that Wa-descended Baekje officials existed in the Yeongsan River basin, while Yukihisa Yamao cited examples in which powerful Wa figures migrated to Baekje and their second-generation sons born with Baekje women became diplomatic envoys, arguing for the existence of such Wa-descended Baekje officials.
The above is from Wikipedia.
Even so, any person with sound judgment is bound to be utterly appalled and exhausted by the conduct of the Koreans.