It has the power to heal Anothers but does not have any effect on humans directly. However, it reacts in presence of Yu-Hwa (because of his crystal) and Yu-Hwa is able to channel its powers to heal a human for a small period of time.
The stone of healing is stolen by Ji-Woon Kang from the Hon. Hon agents pursue him and he ends up with Yu-Hwa. Later it is revealed that Hon has known where Ji-Woon is heading and his purpose. Ji-Woon wanted to use the stone to heal his human grandpa but it has no effect. Yu-Hwa, however, manages to use the stone and heal Ji-Woon's grandpa for a small time, enough for him to have one last chat with his grandson. Later Yu-Hwa hands the stone of healing over to Un.