How was a kampaku different from a regent for a child emperor?

In the context of the Fujiwara family, the primary difference between a regent and a kampaku lies in the age of the emperor they served and the duration of their authority.

• Regent: This position was held by a member of the Fujiwara clan to act on behalf of a child emperor. A significant limitation of the regency was that it typically ended once the emperor reached his majority.1
• Kampaku: Established by Fujiwara Mototsune, the office of kampaku was created to serve as a chief councillor or regent to an adult emperor. By holding this title, the Fujiwara were able to maintain their influence and control over the government even after the emperor had come of age, effectively bypassing the expiration of the regency.21

In practice, both roles allowed the Fujiwara to act as the real center of authority in the government, serving as the emperor's spokesman and the primary intermediary between the throne and the officialdom.21