The medicinal materials required for the production of the Returning Origin Soup are undoubtedly scattered throughout the entirety of the Daming Dynasty, or to put it more precisely, across most of the territories of the Daming Dynasty!
Anybody with normal cognitive abilities and a certain level of logical thinking can deduce this. No investigation is needed for this conclusion.
The number of martial artists is small, however, this is only in comparison to the common population.
Besides, martial artists generally live longer, especially those with higher capabilities.
Therefore, the reality is that martial artists are spread across every inch of the extensive territories of the Daming Empire.
Although the Daming Empire is facing encroachments from alien tribes from all sides and internal insurgencies from bandits, there isn't any major warfare on the whole.