When Gu Ling and Su Liang first met, they exchanged their greatest secrets, Gu Ling's special ability and Su Liang's time-traveling adventure.
At that time, they discussed why Gu Ling should help strangers when he sees the black fog. He is inherently kind, but his kindness is not proactive. Most of the time, he wishes to have nothing to do with outsiders.
He regarded the special ability given to him by heaven as a mission to be fulfilled, not wanting it to disappear due to his own passivity. Because perhaps, after saving one hundred strangers, he would have the chance to save those he cares about, which would be worth it.
Gu Ling initially asked Su Liang to stay by his side to help him with the "missions." Indeed, they rescued some people together.
If mistakes were made, Gu Ling had made them in his childhood when his abilities were limited. Since obtaining high-level martial arts, he has successfully intervened in the lives of those with black fog in their brows.