The "Masukagami" is the last of the four "kagami" history books (books with the word "kagami," or "mirror," in the title), and covers the period from Emperor Go-Toba's enthronement to Emperor Go-Daigo's triumphant return to Kyoto from exile in 1333, focusing on trends within courtly society.
「増鏡」は四鏡の最後の史書で、後鳥羽天皇の即位から1333年に配流となっていた後醍醐天皇が京都に帰還するまでの宮廷社会の動向を記している。