Yama-Kings weren't unkillable, they were just extremely difficult to kill.

Upon sustaining a lethal injury, a Yama-King would be unable to maintain their external form and had to enter a state of slumber. Theoretically speaking, as someone who had eaten the Taisui fungus, Qin Ye should've fared even worse than a normal Yama-King in this situation and automatically entered the Taisui fungus's cycle of reincarnation, but that hadn't happened. 

Right in front of Fernando and Owen's astonished eyes, the wound on Qin Ye's neck was rapidly healing, and color was also beginning to return to his pale cheeks in what was an astonishing recovery.

Qin Ye's throat was in so much pain that he felt as if he were about to go insane. Blood was flowing down onto his chest, giving him quite a terrifying appearance, but he had to maintain a calm smile. 

He had always been searching for an opportunity where his opponent wouldn't be able to evade his attack.

He had thought that this opportunity would be very difficult to find, but Arlot had dug his own grave by creating that inescapable cage of blood. Unfortunately for him, he had played right into Qin Ye's Yellow Emperor Protector Seal!

The victory that he had thought he had secured was nothing more than an illusion, and he had allowed Qin Ye to take one valuable step...