It's all about the Heart Inquiry!
Li Ming wanted Ning Qingman to face the fact—
Back when the Ning Family was destroyed, you were powerless, unable to change anything.
Now that you have reached the Peak and become a Sword Immortal, is it still the same that you can't change anything?
The fall of the Ning Family had always been the deepest scar and emotional knot in Ning Qingman's heart.
Li Ming used Nie Susu to force her to face this emotional knot once more.
Thus, he had the Ming River Ancestor possess everyone in the city with Yin Souls, except for Nie Susu.
If Ning Qingman wished, she could have escaped with Nie Susu alone.
But doing so would mean having Ning Qingman personally take Nie Susu through the same fate she experienced back then!
If Ning Qingman truly did that, she wouldn't have become a Sword Immortal or mastered such swordsmanship.
This was Li Ming's confidence.
Sometimes, the one who knows you best is your enemy.
"I hope you're right."
