Towards the end of the Heian period, it became customary that another "Kurodo no to" post was given to "To no ben" selected from the persons at the Benkan post (a post for civil officers: daiben (Major Controller) or chuben (Middle Controller)).
平安時代末期には弁官（大弁または中弁）から選ばれる頭弁と並びたつ慣例が生まれた。