On the other hand, family registration system based on the ritsuryo system was gradually phased out; in the tenth century, people who became strong among powerful local clans became the retainers of the influential nobles and invaded clan names and hereditary titles; in essence, the phenomenon of so-called Bomei Kain (misrepresentation of one's clan name and hereditary title) became quite commonplace.
一方、律令的戸籍制度も次第に行われなくなり、10世紀には、地方豪族で実力を蓄えた者は、有力な貴族の家人となり、その氏姓を侵すようにさえなり、いわゆる冒名仮蔭（ぼうめいかいん）の現象が一般化した。