The Sonozaki House holds a great deal of influence both inside and outside the village, and was considered to be the leader in movement to stop the dam construction five years before the series starts. They are believed to have been responsible for kidnapping of the grandson of the Minister of Construction, having returned him only after the dam project was put on indefinite hold, but nobody could really prove anything.
They are portrayed as being in some ways similar to traditional yakuza and have a large number of people in their service. These people are often shown in dark glasses and suits, wielding an assortment of weapons like tasers, guns, and swords.
The main family lives in a large, traditional looking house near the river, complete with a garden, a secret torture chamber/dungeon, and an extremely deep well for putting things you don't want found.
Traditionally the first born child inherits the seat of power in the family. Because Akane, Oryō's daughter, married someone unapproved she was denied the right to inherit. There is speculation that it is because of her choice of husband. Regardless, her first-born would then be next in line. The older twin was to be tattooed and raised to take over the family. Traditionally the younger would have been left to die, as twins were long considered bad luck, but they decided not to do so. By some twist of fate they ended up putting the tattoo on the second born by mistake. The marked girl viewers know as Mion was actual the second born and was intended to be named Shion. Only the twins themselves seem to be aware of this.