Thank you for your question!
The easyrpg engine requires the game in ms0.
Hardware PSP
ms0:/PSP/GAME/easyrpg
Place a copy of the game in the PPSSPP's game directory for ms0.
PPSSPP in Windows
%USERPROFILE%/Documents/PPSSPP/PSP/GAME/easyrpg
PPSSPP on Linux
~/.config/ppsspp/psp/game/easyrpg