"Mizu Kagami" (The Water Mirror), "Okagami" (The Great Mirror), "Ima Kagami" (The Mirror of the Present), and "Masu Kagami" (The Clear Mirror) (in order of appearance) are now called 'Shikyo' (the four historical narratives of the late Heian and early Kamakura periods with the word "mirror" in the title), and of these, there is a blank period of time between "Ima Kagami" and "Masu Kagami," which accords with the reigns of both Emperor Takakura and Emperor Antoku.
現在、「四鏡」と呼ばれている『水鏡』・『大鏡』・『今鏡』・『増鏡』（扱った時代順に配列）の中で、『今鏡』と『増鏡』の間に空白の年代があり、それが高倉・安徳両天皇の時代に合致する。