The dataR.cpk file found in Persona 5 Royal contains a GMD model folder, Model (P5R). Each folder is categorized by character ID number. See Model (P5R) for a full list of ID number with character names and descriptions. 4219 refers to Male School Student, and contains 1 GMD model related to him.
|0||c4219_000_00.GMD||School||Outfit worn for school|