The person who entered priesthood for the first time in Japan was an ama, but from the Nara period to the Kamakura period when the placement of a kaidan needed permission from the Imperial Court, all kaidans such as those at Todai-ji Temple and Enryaku-ji Temple were subject to male priests so that it is believed the difficulty of women's jikai (handing down the precepts) and tokudo (entry to the Buddhist priesthood) were related to nyonin kinsei.
そもそも日本で最初の出家者は尼であったが、その戒壇の設置に朝廷の許可が必要であった奈良時代以降、鎌倉時代くらいまで、戒壇の設置を許された東大寺や延暦寺などの戒壇が全て男性僧侶を対象としており、女性（尼）の授戒得度が困難であった点との関連も考えられている。