Even after the Retired Emperor Gotoba was exiled to Oki Province because of the Jokyu no Ran War (1221), he spent eighteen years bringing the collection to a high level of refinement, and issued an Imperial edict, stating that the new collection, which eliminated about 400 poems, was the authentic New Collection of Ancient and Modern Poetry (See 'Okibon with annex').
承久の乱（1221年）により隠岐国に流された後も後鳥羽上皇は十八年の時間をかけて彫琢を加え、新古今和歌集から約400首ほど除いたものこそ正統な新古今和歌集であるという詔を出した（「隠岐本識語」参照）。