What is "mimana"

Mimana , also transliterated as Imna or Yimna according to the Korean pronunciation, is the name used primarily in the 8th-century Japanese text Nihon Shoki, likely referring to one of the Korean states of the time of the Gaya confederacy (c. 1st–5th century) as a territory of ancient Japan. As Atkins notes: "The location, expanse, and Japaneseness of Imna/Mimana remain among the most disputed issues in East Asian historiography." Seth notes that the very existence of Mimana is still disputed.