Inahi no Mikoto
Inahi no Mikoto was a Japanese legendary character. In Japanese traditional mythology, he was a brother of Emperor Jimmu, the first Emperor who according to tradition lived in the 7th century BC. His name Inahi means "boiled rice".
Connections to Korea
According to the Kojiki, he became a king over part of Korea which is speculated to be near the Kaya confederacy.However, according to the Shinsen Shōjiroku, it is stated that he and the kings of Silla shared the same lineage. The kings or their lineages were never specified.
The authenticity of the claim is considered vague and obscure as the record does not specify a name or a dynasty of which the Japanese god became the ancestor to the kings of Silla. However, it is quite likely that the book is alluding to Silla kings who were indeed of Japanese descent such as Talhae of Silla and the grandchild of Heulhae of Silla, who was born from the daughter of Heulhae and the prince of Japan in 312 CE. Interestingly, it is said that Inahi no Mikoto was one of the four sons of Ugayafukiaezu, and with the claim stating that Inahi was the ancestor to the kings of Silla, it can be speculated that Heulhae's grandson was Inahi no Mikoto's child. However, these are historical sources found only in Korea and not in Japan. Moreover, Heulhae's line ended with his successor, Naemul of Silla, who was a Gyeongju Kim clan, which makes the claim of the ownership of the kings of Silla after Heulhae questionable as they descended from different families.
Due to the lack of historical evidence found in Japan, modern Japanese scholars began cross-referencing other sources that may act as a bridge to the claim found in the Shinsen Shōjiroku. According to historian Takehiko Furuta, a legendary Japanese sword called " " had an alternate name called "Orochi no Karasahi "; he posited that "Karasahi " was most likely a loanword from Korean as "Kara " meant "Korea" and "hi " meant "to cut", deriving from the native Korean verb "bi- ; be- " which also means "to cut". Similar observation was made by Furuta on the name "Masahi ", a traditional Japanese horse-riding archery event that has roots in the kingdom of Goguryeo, pointing out that the "hi" found in "Masahi" shares the same sentiment found in "Karasahi".
The kingdom of Goguryeo's founder, Dongmyeong's story was compared with the story found in the Japanese mythology surrounding Inahi no Mikoto by the historian and mythologist, Shōei Mishina. Mishina posited that King Dongmyeong's founding story aligned closely with Inahi no Mikoto's own background; that due to the stories surrounding Inahi no Mikoto and Korea were very similar in nature, he stated that the two were clearly related. His argument was incorporated into the Nissen dōsoron.