The reason Ren Feifan didn't require Old Xu to undress during his treatment was that Old Xu's issue was in his abdomen. Ren Feifan could direct True Qi to the Evil Qi in the abdomen through some acupoints on the body!
Moreover, that mass of Evil Qi hadn't approached Elder Ye's critical areas. However, it was different for Ye Qingcheng. The Evil Qi inside Ye Qingcheng loitered around her chest, near her heart! If they weren't careful, her life would be in danger!
The key was that the Evil Qi couldn't be forcefully expelled through the use of True Qi as it could inevitably harm Ye Qingcheng's heart!
"Aren't you going to speak?! Can't believe a man can be so hesitant..." Ye Qingcheng was somewhat irritated. She couldn't understand why Ren Feifan was stammering at this critical juncture of her treatment, as if he were hiding something!
"Do you really want to know?" Ren Feifan asked with a devilish grin at the corner of his mouth.