How to upgrade medicine in Phantom Blade Zero

In Phantom Blade Zero, you can upgrade your medicine at the Green Serpent House in west Pangzhen using healer's memories, improving the HP percentage, damage negation, and Sha-Chi it replenishes. You reach the location during Pangzhen's second chapter after defeating Xie Qiudong, The Divine Healer, and your first visit also grants the Green Serpent Brew, which removes status effects.