How does Shi-Woon regenerate his wounds so fast?
His regeneration and stamina have been greatly enhanced thanks to the extremely rare and expensive pill that Lee Shi-Ho (whose clan specialises in such matters) gives him. The pill, Illwallsidan, triggers a tremendous release of ki which most people cannot handle (and often die). But thanks to Chun-Woo's timely assistance, Shi-Woon somehow manages.

Much of New Waves tackles how Shi-Woon goes about restoring his broken ki centre.