Mufeng had never once intended to fight Jiang Qing in a direct duel. A boss-tier monster had a health bar so long that dragging out a fight would be a terrible waste of time, not to mention bad for building a relationship.
His initial use of the Huashan Sword Technique was primarily to let Jiang Qing understand his strength. Only once one's strength was acknowledged could conversation begin.
Take right now, for instance. Jiang Qing was left speechless, the entire initiative firmly in Mufeng's hands.
Chapter 71