In Japanese Tendai, the lineages of the Garbhadhātu and Vajradhātu each have two parts 両部各別. The first appearance of a samaya ritual manual in Tendai is the Nyūmandara jubosatsukai gyōgi 入曼荼羅受菩薩戒行儀 of Genjō 玄静 （fl. around 904）. The samaya ritual manuals imported from China were not categorized into garbha and vajra （両部）, so the content is very different from Genjō’s ritual manual.
However, at the same time that the differentiated two part ritual of Garbha and Vajra appeared, the conjoined Garbha and Vajra ritual 両部合行 was created. Investigation of the date of establishment of the two-part conjoined ritual reveals the involvement of Kōgei 皇慶 （977?-1049） in its creation.
In addition, the samaya ritual manuals made in China and Japan have different personalities. Japanese ritual manuals were prepared so that they could be used as handy guides in the ritual of initiation.
