This seal is given to all branch house members in the Hyuga clan by members of the main house. Its main purpose is to seal their Byakugan ability when they die, preventing an enemy from learning its secrets.Its secondary purpose is to control the branch house, since it can be activated at will by a main house member with a hand seal that only they know about.The seal is placed on the wearer's forehead when the next member of the main house turns three years old, (Neji Hyuga received his at the age of four on Hinata's third birthday), and is only removed upon their death. Branch house members keep their foreheads covered because of the seal.