He must preserve the soul fragment within him, and likewise, he must save the person Gu Sheng.
Consider it a return of the favor to that person.
After Nie Jiuque saved the life of Gu Yao, he fed her medicine.
At the sound of a disturbance, Nie Jiuque was startled. Just as he was about to take the two away, he heard the voice of the newcomer clearly.
Thus, relieved, he left Gu Yao behind and, taking Gu Sheng and Ye Yin, vanished into the darkness.
In the pitch-black alley, Gu Li only found Gu Yao. Upon discovering Gu Yao was still alive, he immediately sent her to the hospital for emergency treatment.
"Master, did you save Gu Yao and Gu Sheng because of Gu Li?"
Ye Yin asked with furrowed brows.
The master could have simply extracted the soul fragment from Gu Sheng and kept it safely. Why expend energy to save their lives?
Nie Jiuque said nothing. After withdrawing his gaze from Gu Li, he took Gu Sheng back to the secret chamber.