Isshi-100

The Isshi-20 (イッシー20) are the twenty most skilled doctors of Drum Island, whom Wapol took for himself in order to make his subjects grovel at his feet for their services.

They are skilled enough to save Wapol's life even after he has been decapitated. While they were under Wapol's control, they secretly despised and hated him as the rest of the people did. However, they gave in to the King in order to continue their research and refine their technique. Upon seeing the quack, Dr. Hiluluk's, noble sacrifice, the Isshi-20 has determined to never lose to the quack. To this end, they hoped to use their research and techniques to help their compatriots. After Wapol was defeated, they were forgiven by the people of the island and rejoined them as part of the new Sakura Kingdom.

Translation and Dub Issues
"Isshi" is derived from "Ishi" (医師), which means "doctor". In the English version, the Isshi-20 are accurately translated as "doctors" or "MDs", meaning medical doctor.