The Yin Seal: Release is a powerful sealing technique used by Tsunade and Sakura. Over a period of time, the user focuses and builds up chakra in the seal mark on their forehead. The release command disperses the seal and allows the stored chakra to pump back into the users body. Tsunade used this stored chakra to perform the Creation Rebirth technique on herself and healed a vast amount of people through Katsuyu. Tsunade and Sakara are also able to use the Strength of a Hundred Technique after releasing the seal.
After using the chakra from the Yin Seal for her techniques, if there is any leftover chakra, Tsunade may use it to re-form the seal as she did after her fight with Orochimaru.
Tsunade's grandmother, Mito Uzumaki, had a similar diamond-shaped mark on her forehead. Although it is believed that Tsunade's seal was modelled after the mark, it is unknown whether her grandmother was able to use the same technique or not.