Passage: In Japan, Sesshō (摂政) was a title given to a regent who was named to act on behalf of either a child Emperor before his coming of age, or an empress regnant. The Kanpaku (関白) was theoretically a sort of chief advisor for the Emperor, but was the title of both first secretary and regent who assists an adult Emperor. During a certain period in the Heian period, they were the effective rulers of Japan. There was little, if any, effective difference between the two titles, and several individuals merely changed titles as child Emperors grew to adulthood, or adult Emperors retired or died and were replaced by child Emperors. The two titles were collectively known as Sekkan (摂関), and the families that exclusively held the titles were called Sekkan-ke or Sekkan family. After the Heian period, shogunates took over the power.

Question: What is the name of the person who acts on the behalf of a child Emperor before they become an adult?
Sesshō