Although they felt like the two can't stay together, King Jin and Muxin had to set aside their differences. Yi Ling needed to go inside the Blue Rose Palace. Since the seals are on her soul, it was the best way to unlock it when she's inside the Sapphire Jade Ring.
As King Jin's suggestion, Ye Fang and Qianru were left outside to take care of Yi Ling's body. Of course, King Jin and Muxin also coordinated to make sure that Yi Ling would be safe. Muxin set up a barrier around the cave while King Jin set up traps and detectors outside the cave. If an enemy tries to come in, King Jin could always get out and handle it. Well, only when Yi Ling's subordinates couldn't handle it.
