From the end of the Heian period into the Kamakura period, influenced by internal strife and ryoto tetsuritsu (alternate accedence from two ancestries of imperial families), there was a flood of use of the Nyoin title, and at one time the number of Nyoin was in the tens.
平安末期から鎌倉時代にかけて、内乱や両統迭立に影響され、女院号の宣下が氾濫し、一時には十数人にのぼる女院がいた。