Mu Lingxi was able to become the Saintess of the Demonic Sect and infiltrate the Martial City Academy for so long. It was evident that she was very smart and strategic.
Thus, she could naturally see that Qiu Yu was purposely using "kindness" to threaten her.
If she'd really softened and freed Qiu Yu, then today would probably be the day of Zhang Ruochen and Le's deaths.
Qiu Yu could see the worry in Mu Lingxi's heart. "Lingxi," he quickly said. "Don't worry. I swear that as long as you free, I definitely won't take revenge on Zhang Ruochen. You should know that, for top cultivators, going against their word would affect their mindset greatly."
Holding her sword, Mu Lingxi walked over and pointed it to Qiu Yu's forehead. "No need to speak further. Since I said I'll ask forgiveness from Zhang Ruochen, I will definitely try my best to save you."