Consuming a lot of True Qi and might not succeed, Li Yifei was well aware of these facts. However, under the watchful eyes of the crowd, he must save the young boy.
The difficulty lay in the fact that there was also a strand of Evil Qi within the boy, and it was a self-conscious Evil Qi that would hide. This hiding process could harm the boy's body and, in the end, might cause the Evil Qi to go for broke, destroying the host even at the cost of annihilating itself.
But Li Yifei had already devised a countermeasure. He began by sealing the boy's head with True Qi to prevent the Evil Qi from entering the brain, then protected the heart. As for other parts... he believed they were not much to worry about.
The Evil Qi crashed around, only to eventually find itself surrounded. Helplessly, it chose to self-destruct, but was instead cornered by the prepared Li Yifei. Of course, even so, it caused significant distress to the young boy, with some damage to his internal organs.
