karate practitioner; karateka
Refers to a person who practices karate, often with a connotation of dedication or expertise.
He is a famous karate practitioner and won the world championship.
Using his experience as a karateka, he teaches children.
Compound of 空手 (karate) and 家 (-ka, 'person who does something'). The suffix 家 is commonly used to denote a practitioner or expert in a field.