The reason why the position of a legally wedded wife was so strong is that a nobleman married his bride to enter her family, and therefore, his residence was originaly owned by her family.
正室の地位がこのように高かったのは、当時の貴族は基本的に婿取婚だったため、彼らの邸宅はそもそも正室の実家が所有するものに他ならなかったからである。